Variable Interest Entities - Principal Provisions of Debt (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2014		Dec. 31, 2013
Debt Instrument [Line Items]
Principal Outstanding	$ 12,953,960		$ 12,840,843
Senior Secured Notes
Debt Instrument [Line Items]
Principal Outstanding	12,006,603	[1],[2]	11,877,744	[1],[2]
Weighted Average Interest Rate	1.33%	[1],[2]	1.31%	[1],[2]
Weighted Average Remaining Maturity in Years	7 years 3 months 18 days	[1],[2]	7 years 3 months 18 days	[1],[2]
Subordinated Notes
Debt Instrument [Line Items]
Principal Outstanding	$ 947,357	[1],[2]	$ 963,099	[1],[2]
Weighted Average Remaining Maturity in Years	8 years 1 month 6 days	[1],[2]	8 years 1 month 6 days	[1],[2]

[1] The debt at fair value of the consolidated VIEs is collateralized by assets of the consolidated VIEs and assets of one vehicle may not be used to satisfy the liabilities of another vehicle. As of March 31, 2014 and December 31, 2013, the fair value of the consolidated VIE assets was $15,960 million and $15,502 million, respectively. This collateral consisted of cash and cash equivalents, investments, at fair value, and other assets.

[2] The fair value of Senior Secured Notes and Subordinated Notes as of March 31, 2014 and December 31, 2013 was $12,528 million and $12,424 million, respectively.