Earnings Per Common Share - Summary of Earnings Per Common Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Numerator for both basic and diluted earnings per common share:
Net income available to common shareholders	$ 68,057	$ 4,488	$ 138,641	$ 27,884
Denominator:
Total average basic common shares outstanding	66,894,398	67,104,628	67,078,036	67,295,589
Effect of dilutive stock options and other stock compensation	172,194	77,127	161,512	114,871
Total diluted average common shares outstanding	67,066,592	67,181,755	67,239,548	67,410,460
Earnings per common share - basic	$ 1.02	$ 0.07	$ 2.07	$ 0.41
Earnings per common share - diluted	$ 1.01	$ 0.07	$ 2.06	$ 0.41