Variable Interest Entities - Carrying Amounts of Assets and Liabilities (Parenthetical) (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Variable Interest Entity [Line Items]
Investments	$ 2,640,676,000	$ 2,393,883,000
Cumulative revenues recognized if existing investments become worthless	4,904,000,000	4,858,000,000
Variable Interest Entities
Variable Interest Entity [Line Items]
Cash	278,131,000	354,686,000
Investments	11,622,052,000	12,034,487,000
Receivables	731,476,000	477,325,000
Debt and other payables	608,225,000	1,161,549,000
Securities sold	150,658,000	106,532,000
Capital withdrawals payable	$ 3,628,000	$ 43,198,000