Earnings Per Share Reconciliation - Schedule of Earnings Per Common Share Reconciliation (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 common share:
Net earnings	$ 28,373	$ 25,514	$ 56,877	$ 48,905
Less: Net earnings allocated to restricted stock	105	99	217	205
Net earnings allocated to common shareholders	$ 28,268	$ 25,415	$ 56,660	$ 48,700
Weighted average shares outstanding	109,730	108,834	109,039	106,917
Basic earnings per common share	$ 0.26	$ 0.23	$ 0.52	$ 0.46
Diluted earnings per common share:
Net income allocated to common shareholders	$ 28,268	$ 25,415	$ 56,660	$ 48,700
Weighted average shares outstanding	109,730	108,834	109,039	106,917
Incremental shares from assumed exercise of outstanding options	348	410	406	406
Diluted weighted average shares outstanding	110,078	109,244	109,445	107,323
Diluted earnings per common share	$ 0.26	$ 0.23	$ 0.52	$ 0.45