HA Sustainable Infrastructure Capital, Inc. Annual report pursuant to Section 13 and 15(d)

Financing Receivables and Investments - Analysis of Financing Receivables and Investments by Type of Obligor and Credit Quality (Detail)

Financing Receivables and Investments - Analysis of Financing Receivables and Investments by Type of Obligor and Credit Quality (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Sep. 30, 2012
Financing Receivable, Recorded Investment [Line Items]
Financing receivables	$ 347,800,000
Investments	91,964,000
Financing receivables and investments held-for-sale	28,000,000
Total	467,800,000
% of Total Portfolio	100.00%
Average Remaining Balance	14,000,000
Federal [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables	229,800,000
Investments
Financing receivables and investments held-for-sale	24,800,000
Total	254,600,000
% of Total Portfolio	55.00%
Average Remaining Balance	10,900,000
State, Local, Institutions [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables	73,300,000
Investments
Financing receivables and investments held-for-sale
Total	73,300,000
% of Total Portfolio	16.00%
Average Remaining Balance	24,400,000
Commercial Externally Rated [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables
Investments	76,900,000
Financing receivables and investments held-for-sale
Total	76,900,000
% of Total Portfolio	16.00%
Average Remaining Balance	25,600,000
Commercial Rated Internally [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables	43,900,000
Investments
Financing receivables and investments held-for-sale
Total	43,900,000
% of Total Portfolio	9.00%
Average Remaining Balance	21,900,000
Commercial Other [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing receivables	800,000
Investments	15,100,000
Financing receivables and investments held-for-sale	3,200,000
Total	19,100,000
% of Total Portfolio	4.00%
Average Remaining Balance	$ 9,200,000