Investments Summary of Investment in Private Equity Funds (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	$ 76,593	$ 67,560
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	35,635	32,379
ECP II [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	2,910	3,251
Discovery Fund [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	2,673	5,015
EMCP II [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	12,584	11,125
EMCP III [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	7,264	3,852
CSI Capital [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	3,778	3,248
Trilantic IV [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	3,812	4,356
Trilantic V [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	$ 2,614	$ 1,532