Investments - Net Gains from Investment Activities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Gain (Loss) on Investments [Line Items]
Realized gains on sales of investments	$ 167	$ 45	$ 408	$ 136
Change in net unrealized gains (losses) due to changes in fair values	949	(28,259)	52,841	129,358
Net Gains (Losses) from Investment Activities	1,116	(28,214)	53,249	129,494
Private Equity Segment [Member]
Gain (Loss) on Investments [Line Items]
Change in net unrealized gains (losses) due to changes in fair values	7,064	(15,149)	54,833	138,543
Net Gains (Losses) from Investment Activities	7,064	(15,149)	54,833	138,543
Credit [Member]
Gain (Loss) on Investments [Line Items]
Realized gains on sales of investments	167	45	408	136
Change in net unrealized gains (losses) due to changes in fair values	(6,115)	(13,110)	(1,992)	(9,185)
Net Gains (Losses) from Investment Activities	$ (5,948)	$ (13,065)	$ (1,584)	$ (9,049)

- Definition

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

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