Quarterly report pursuant to Section 13 or 15(d)

Financing receivables and Investments - Additional Information (Detail)

v2.4.0.8
Financing receivables and Investments - Additional Information (Detail) (USD $)
9 Months Ended 9 Months Ended 1 Months Ended 3 Months Ended 9 Months Ended
Sep. 30, 2013
Dec. 31, 2012
Sep. 30, 2013
Berkshire Hathaway Inc. [Member]
Sep. 30, 2013
Exelon Corporation [Member]
May 31, 2013
HA EnergySource [Member]
Sep. 30, 2013
HA EnergySource [Member]
Sep. 30, 2013
HA EnergySource [Member]
Noncancelable Obligations Future Minimum Payments Due [Line Items]              
Deferred funding obligations $ 77,200,000            
Restricted cash 38,927,000 55,000          
Notes receivable - related party         24,000,000 24,800,000 24,800,000
Interest rate of related party loan         15.22% 6.50%  
Maturity period of related party loan         May 31, 2018    
Interest paid on the loan           400,000 600,000
Loan proceeds not spent - related party           14,000,000 14,000,000
Debt security, carrying value     37,000,000 35,000,000      
Debt security, maturity year     2035 2033      
Financing receivable held for sale , carrying value and fair value $ 21,138,000            
Amortizing government receivables maturity date 2038-02-28