Investments - Other Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Other investments, at fair value	$ 953,991	$ 1,034,032
Other
Investment Holdings [Line Items]
Other investments, at fair value	1,136	1,144
Private equities and private equity funds
Investment Holdings [Line Items]
Other investments, at fair value	249,398	254,883
Fixed income funds
Investment Holdings [Line Items]
Other investments, at fair value	267,839	291,736
Fixed income hedge funds
Investment Holdings [Line Items]
Other investments, at fair value	109,636	109,400
Equity funds
Investment Holdings [Line Items]
Other investments, at fair value	150,348	147,390
Multi-strategy hedge fund
Investment Holdings [Line Items]
Other investments, at fair value	98,432	99,020
Real estate debt fund
Investment Holdings [Line Items]
Other investments, at fair value	0	54,829
CLO equities
Investment Holdings [Line Items]
Other investments, at fair value	58,975	61,702
CLO equity funds
Investment Holdings [Line Items]
Other investments, at fair value	12,167	13,928
Call options on equities
Investment Holdings [Line Items]
Other investments, at fair value	$ 6,060	$ 0