Earnings Per Share - Reconciliation of Numerator and Denominator of Basic Earnings Per Share with that of Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share [Abstract]
Distributed earnings allocated to common stock	$ 45,298	$ 34,604	$ 80,785	$ 69,276
Undistributed earnings allocated to common stock	7,262	32,446	11,840	61,276
Net earnings allocated to common shareholders	$ 52,560	$ 67,050	$ 92,625	$ 130,552
Average common shares outstanding	119,823,652	101,773,643	110,559,363	101,833,880
Equivalents from stock options	64,171	274,202	65,613	265,929
Average diluted shares outstanding	119,887,823	102,047,845	110,624,976	102,099,809
Earnings per basic common share	$ 0.44	$ 0.66	$ 0.84	$ 1.28
Earnings per diluted common share	$ 0.44	$ 0.66	$ 0.84	$ 1.28