Basis of Presentation and Significant Accounting Policies - Summary of Table Reconciling Basic and Diluted Net Income Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Basic Earnings Per Share, Weighted average common shares outstanding									137,821	127,705	115,726
Basic Net Income Per Share	$ (0.13)	$ 0.30	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1.01
Net income	$ (18,493)	$ 39,372	$ 38,854	$ 35,992	$ 33,456	$ 34,709	$ 39,122	$ 26,977	$ 95,725	$ 134,264	$ 116,716
Diluted Earnings Per Share, Weighted average common shares outstanding									137,821	127,705	115,726
Effect of dilutive securities: Restricted stock									599	543	440
Effect of dilutive securities: Stock options									93	53	89
Diluted Earnings Per Share, Weighted average shares outstanding	146,875	135,796	135,697	135,431	135,383	135,011	127,973	114,563	138,513	128,301	116,255
Diluted Earnings Per Share	$ (0.13)	$ 0.29	$ 0.28	$ 0.27	$ 0.25	$ 0.25	$ 0.31	$ 0.24	$ 0.69	$ 1.05	$ 1.00