Summary of Investment in Private Equity Funds (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	$ 69,320	$ 68,230
Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	26,578	25,151
ECP II | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	3,793	5,037
Discovery Fund | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	3,060	2,393
EMCP II | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	10,400	9,674
EMCP III | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	1,696
CSI Capital | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	3,056	3,496
Trilantic IV | Private Equity Funds
Schedule of Equity Method Investments [Line Items]
Total Private Equity Funds	$ 4,573	$ 4,551