Stock-Based Compensation - Summary of Share Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Stock-based compensation expense:
Total stock-based compensation expense	$ 1,406	$ 1,640	$ 2,896	$ 3,359
Time-based Restricted Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	597	571	1,216	1,208
Performance-based Restricted Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	$ 809	$ 1,069	$ 1,680	$ 2,151