Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 25,951	$ 31,399	$ 24,393	$ 30,890	$ 35,763	$ 35,468	$ 19,243	$ 27,913	$ 112,633	$ 118,387	$ 93,949
Basic weighted average common shares outstanding (in shares)									64,604,224	64,942,886	64,384,851
Dilutive shares (in shares)									130,367	160,211	194,371
Diluted weighted average common shares outstanding (in shares)									64,734,591	65,103,097	64,579,222
Earnings per share:
Basic (in dollars per share)	$ 0.40	$ 0.49	$ 0.38	$ 0.48	$ 0.55	$ 0.55	$ 0.30	$ 0.43	$ 1.74	$ 1.82	$ 1.46
Diluted (in dollars per share)	$ 0.40	$ 0.49	$ 0.38	$ 0.48	$ 0.55	$ 0.54	$ 0.30	$ 0.43	$ 1.74	$ 1.82	$ 1.45
Anti-dilutive stock options and awards excluded from computation of earnings per share (in shares)									646,457	443,748	369,772