Earnings Per Share - Reconciliation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share [Abstract]
Net income	$ 1,302	$ 19,013	$ 36,137	$ 36,769	$ 48,354	$ 50,777	$ 39,213	$ 53,664	$ 93,221	$ 192,008	$ 208,712
Weighted average basic common shares outstanding (in shares)									37,537	38,364	39,964
Effect of dilutive securities-stock options and awards (in shares)									130	167	226
Total shares and dilutive securities (in shares)									37,667	38,531	40,190
Basic earnings per common share (in dollars per share)	$ 0.03	$ 0.51	$ 0.96	$ 0.97	$ 1.28	$ 1.32	$ 1.01	$ 1.38	$ 2.48	$ 5.00	$ 5.22
Diluted earnings per common share (in dollars per share)	$ 0.03	$ 0.51	$ 0.96	$ 0.97	$ 1.28	$ 1.32	$ 1.01	$ 1.38	$ 2.47	$ 4.98	$ 5.19