Investments Summary of Investment in Private Equity Funds (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Private Equity Funds [Member]	Dec. 31, 2012 Private Equity Funds [Member]	Sep. 30, 2013 ECP II [Member] Private Equity Funds [Member]	Dec. 31, 2012 ECP II [Member] Private Equity Funds [Member]	Sep. 30, 2013 Discovery Fund [Member] Private Equity Funds [Member]	Dec. 31, 2012 Discovery Fund [Member] Private Equity Funds [Member]	Sep. 30, 2013 EMCP II [Member] Private Equity Funds [Member]	Dec. 31, 2012 EMCP II [Member] Private Equity Funds [Member]	Sep. 30, 2013 EMCP III [Member] Private Equity Funds [Member]	Dec. 31, 2012 EMCP III [Member] Private Equity Funds [Member]	Sep. 30, 2013 CSI Capital [Member] Private Equity Funds [Member]	Dec. 31, 2012 CSI Capital [Member] Private Equity Funds [Member]	Sep. 30, 2013 Trilantic IV [Member] Private Equity Funds [Member]	Dec. 31, 2012 Trilantic IV [Member] Private Equity Funds [Member]	Sep. 25, 2013 Trilantic V [Member]	Sep. 30, 2013 Trilantic V [Member] Private Equity Funds [Member]	Dec. 31, 2012 Trilantic V [Member] Private Equity Funds [Member]
Schedule of Equity Method Investments [Line Items]
Investment in private equity funds	$ 62,223	$ 69,320	$ 33,378	$ 26,578	$ 3,384	$ 3,793	$ 5,098	$ 3,060	$ 10,425	$ 10,400	$ 3,815	$ 1,696	$ 2,918	$ 3,056	$ 6,727	$ 4,573	$ 1,038	$ 1,011	$ 0