Investments - Other Investments (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Investment Holdings [Line Items]
Other investments, at fair value	$ 1,034,032	$ 836,868
Other
Investment Holdings [Line Items]
Other investments, at fair value	1,144	3,698
Private equities and private equity funds
Investment Holdings [Line Items]
Other investments, at fair value	254,883	197,269
Fixed income funds
Investment Holdings [Line Items]
Other investments, at fair value	291,736	335,026
Fixed income hedge funds
Investment Holdings [Line Items]
Other investments, at fair value	109,400	59,627
Equity funds
Investment Holdings [Line Items]
Other investments, at fair value	147,390	150,053
Multi-strategy hedge fund
Investment Holdings [Line Items]
Other investments, at fair value	99,020	0
Real estate debt fund
Investment Holdings [Line Items]
Other investments, at fair value	54,829	33,902
CLO equities
Investment Holdings [Line Items]
Other investments, at fair value	61,702	41,271
CLO equity funds
Investment Holdings [Line Items]
Other investments, at fair value	$ 13,928	$ 16,022