Investments - Other Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Other investments recorded in private equities	$ 646,765	$ 569,293
Private Equity Funds [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	191,452	161,229
Fixed Income Funds [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	222,004	194,375
Fixed Income Hedge Funds [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	69,547	68,157
Equity Funds [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	128,110	109,355
Real Estate Debt Fund [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	32,469	32,113
Other [Member]
Investment Holdings [Line Items]
Other investments recorded in private equities	$ 3,183	$ 4,064