Net Income per Share - Reconciliation of Basic to Diluted Net Income per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Net income	$ 15,384	$ 9,349	$ 25,710	$ 18,159
Shares used in net income per common share - basic (in shares)	28,978	25,699	28,873	25,699
Dilutive effect of the equity premium on Convertible Notes at the average price of common stock (in shares)		232		9
Incremental shares of unvested restricted common stock (in shares)	136	37	169	85
Shares used in net income per common share - diluted (in shares)	29,114	25,968	29,042	25,793
Basic net income	$ 0.53	$ 0.36	$ 0.89	$ 0.71
Diluted net income	$ 0.53	$ 0.36	$ 0.89	$ 0.70