Stock-Based Compensation - Summary of Share Based Compensation Expense (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Stock-based compensation expense:
Total stock-based compensation expense	$ 1,719	$ 688
Time-based Restricted Stock Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	637	127
Performance-based Restricted Stock Units [Member]
Stock-based compensation expense:
Total stock-based compensation expense	$ 1,082	$ 561