Treasury Stock - Additional Information (Detail) - USD ($)	12 Months Ended			96 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015
Equity Class Of Treasury Stock [Line Items]
Common stock amount authorized under repurchase program, value	$ 93,100,000			$ 93,100,000
Stock repurchased during period (in shares)	96,277	773,635		6,168,549
Average stock price of shares repurchased (in dollars per share)	$ 17.66	$ 16.52		$ 9.23
Purchase of treasury stock	$ 1,704,000	$ 12,809,000	$ 12,025,000	$ 57,200,000
Maximum
Equity Class Of Treasury Stock [Line Items]
Common stock amount authorized under repurchase program, value			$ 150,000,000.0