Stock-Based Compensation - Summary of Share Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stock-based compensation expense:
Total stock-based compensation expense	$ 1,454	$ 1,700	$ 4,349	$ 5,059
Time-based Restricted Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	631	619	1,847	1,827
Performance-based Restricted Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	$ 823	$ 1,081	$ 2,502	$ 3,232