Investments - Net Gains from Investment Activities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Gain (Loss) on Investments [Line Items]
Realized gains on sales of investments	$ 112	$ 242
Change in net unrealized gains due to changes in fair values	223,296	51,891
Net Gains from Investment Activities	223,408	52,133
Private Equity Funds
Gain (Loss) on Investments [Line Items]
Realized gains on sales of investments	0	0
Change in net unrealized gains due to changes in fair values	205,363	47,770
Net Gains from Investment Activities	205,363	47,770
Credit
Gain (Loss) on Investments [Line Items]
Realized gains on sales of investments	112	242
Change in net unrealized gains due to changes in fair values	17,933	4,121
Net Gains from Investment Activities	$ 18,045	$ 4,363