Share Repurchases - Summary of Share Repurchases under Stock Repurchase Plan (Detail) - USD ($)	12 Months Ended		20 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	May. 01, 2014
Equity [Abstract]
Authorized, shares	0		0
Authorized, amount	$ 50,000,000		$ 50,000,000	$ 25,000,000
Repurchases, shares	0	464	755,310
Repurchases, amount			$ (16,627,000)
Remaining authorization, shares	0		0
Remaining authorization, amount	$ 33,373,000		$ 33,373,000