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 (Parenthetical) (Detail)

v2.4.0.8
Financing Receivables and Investments - Analysis of Financing Receivables and Investments by Type of Obligor and Credit Quality (Parenthetical) (Detail) (USD $)
 12 Months Ended
Dec. 31, 2013
Transactions
Financing Receivable, Recorded Investment [Line Items]  
Total financing receivable $ 17,700,000
Financing receivable due greater than 90 days 1,300,000
Allowance for credit losses 11,000,000
Number of transactions 14
Financial receivable outstanding, Average Remaining Balance 14,000,000
Total aggregate remaining balance 5,500,000
Berkshire Hathaway Inc [Member]
  
Financing Receivable, Recorded Investment [Line Items]  
Debt security, carrying value 37,000,000
Debt security, maturity 2035
Exelon Corporation [Member]
  
Financing Receivable, Recorded Investment [Line Items]  
Debt security, carrying value 35,000,000
Debt security, maturity 2033
NRG Energy [Member]
  
Financing Receivable, Recorded Investment [Line Items]  
Allowance for credit losses 11,000,000
Senior debt investment $ 15,100,000