Fair Value Measurements - Schedule of Fair Value Measurements for Level 3 Assets (Detail) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Beginning balance	$ 1,680	$ 2,372
Net gains included in earnings	31,400	21,709
Settlements	$ (33,080)	(22,401)
Ending balance		$ 1,680