Earnings Per Common Share (Earnings Per Share Basic And Diluted) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ 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 Reconciliation [Abstract]
Net income	$ 90,473	$ 93,865	$ 98,649	$ 99,736	$ 98,838	$ 99,673	$ 81,682	$ 80,225	$ 382,723	$ 360,418	$ 255,439
Less: Preferred stock dividends									7,875	7,853	8,184
Net income available to common shareholders, basic										352,565	247,255
Net income available to common shareholders, diluted									374,848	352,565	247,255
Less: Earnings applicable to participating securities, basic									1,863	862	424
Less: Earnings applicable to participating securities, diluted									1,863	862	424
Earnings applicable to common shareholders	$ 88,066	$ 91,442	$ 96,193	$ 97,549	$ 96,666	$ 97,460	$ 79,489	$ 78,083	372,985	351,703	246,831
Earnings applicable to common shareholders, diluted									$ 372,985	$ 351,703	$ 246,831
Earnings per common share:
Earnings per common share, Basic (in dollars per share)	$ 0.96	$ 1.00	$ 1.05	$ 1.06	$ 1.05	$ 1.06	$ 0.87	$ 0.85	$ 4.07	$ 3.83	$ 2.68
Earnings per common share, Diluted (in dollars per share)	$ 0.96	$ 1.00	$ 1.05	$ 1.06	$ 1.05	$ 1.06	$ 0.86	$ 0.85	$ 4.06	$ 3.81	$ 2.67
Weighted Average Number of Shares Outstanding Reconciliation [Abstract]
Weighted-average common shares outstanding - basic									91,559	91,930	91,965
Stock options and restricted stock (in shares)									323	297	391
Weighted Average Number of Shares Outstanding, Diluted									91,882	92,227	92,356