Fair Values - Reconciliation of Beginning and Ending Balances of Assets Measured at Fair Value on Recurring Basis Using Level 3 Inputs (Detail) - Level 3 [Member] - Recurring [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance, beginning	$ 47,507	$ 54,461
Proceeds from investment realizations	(57,039)	(20,231)
Adjustments to fair value included in earnings
Gain on investments at fair value	22,093	13,277
Balance, ending	$ 12,561	$ 47,507