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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Earnings per common share:
Net earnings	$ 25,514	$ 26,813	$ 48,905	$ 42,646
Less: Net earnings allocated to restricted stock	99	143	205	223
Net earnings allocated to common shareholders	$ 25,415	$ 26,670	$ 48,700	$ 42,423
Weighted average shares outstanding	108,834	105,707	106,917	105,616
Basic earnings per common share	$ 0.23	$ 0.25	$ 0.46	$ 0.40
Diluted earnings per common share:
Net income allocated to common shareholders	$ 25,415	$ 26,670	$ 48,700	$ 42,423
Weighted average shares outstanding	108,834	105,707	106,917	105,616
Incremental shares from assumed exercise of outstanding options	410	451	406	445
Diluted weighted average shares outstanding	109,244	106,158	107,323	106,061
Diluted earnings per common share	$ 0.23	$ 0.25	$ 0.45	$ 0.40