Annual report pursuant to Section 13 and 15(d)

Fair Value Measurements - Schedule of Fair Values of Retained Assets, Discount Rates Used in Valuing Assets (Detail)

v2.4.1.9
Fair Value Measurements - Schedule of Fair Values of Retained Assets, Discount Rates Used in Valuing Assets (Detail) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Servicing Assets at Fair Value [Line Items]    
Discount rate 8.00%us-gaap_FairValueInputsDiscountRate  
Servicing [Member]    
Servicing Assets at Fair Value [Line Items]    
Amortized cost basis $ 1.0hasi_RetainedInterestAmortizedCostBasis
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
$ 1.3hasi_RetainedInterestAmortizedCostBasis
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
Fair value 1.2us-gaap_RetainedInterestFairValueDisclosure
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
1.4us-gaap_RetainedInterestFairValueDisclosure
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
Weighted-average life in years 9 years 8 years
Discount rate 8.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
8.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
Fair value that would be decreased based on hypothetical adverse changes in discount rates:    
5% change in discount rate 0.2hasi_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfFivePercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
0.3hasi_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfFivePercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
10% change in discount rate 0.4us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
0.4us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ServicingMember
Residual Assets [Member]    
Servicing Assets at Fair Value [Line Items]    
Amortized cost basis 5.1hasi_RetainedInterestAmortizedCostBasis
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
4.8hasi_RetainedInterestAmortizedCostBasis
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
Fair value 5.2us-gaap_RetainedInterestFairValueDisclosure
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
4.9us-gaap_RetainedInterestFairValueDisclosure
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
Discount rate 8.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
 
Fair value that would be decreased based on hypothetical adverse changes in discount rates:    
5% change in discount rate 1.5hasi_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfFivePercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
1.2hasi_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOfFivePercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
10% change in discount rate $ 2.3us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
$ 1.8us-gaap_SensitivityAnalysisOfFairValueOfInterestsContinuedToBeHeldByTransferorServicingAssetsOrLiabilitiesImpactOf10PercentAdverseChangeInDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
Residual Assets [Member] | Minimum [Member]    
Servicing Assets at Fair Value [Line Items]    
Weighted-average life in years 7 years 6 years
Discount rate   8.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
Residual Assets [Member] | Maximum [Member]    
Servicing Assets at Fair Value [Line Items]    
Weighted-average life in years 19 years 19 years
Discount rate   10.00%us-gaap_FairValueInputsDiscountRate
/ us-gaap_FinancialInstrumentAxis
= hasi_ResidualAssetsMember
/ us-gaap_RangeAxis
= us-gaap_MaximumMember