Investments Summary of Investment in Private Equity Funds (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	$ 86,287	$ 76,581
Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	26,473	36,551
ECP II [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	983	4,043
Discovery Fund [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	6,632	2,867
EMCP II [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	6,091	12,630
EMCP III [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	5,786	7,272
CSI Capital [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	35	3,030
Trilantic IV [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	2,829	3,798
Trilantic V [Member] | Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	$ 4,117	$ 2,911