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, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Earnings Per Share Reconciliation [Abstract]
Net income	$ 57,660	$ 51,817	$ 50,603	$ 47,047	$ 51,812	$ 51,370	$ 52,043	$ 49,504	$ 207,127	$ 204,729	$ 199,726
Less: Preferred stock dividends									8,096	8,711	10,556
Net income available to common shareholders, basic	$ 55,501	$ 49,634	$ 48,398	$ 44,921	$ 49,646	$ 49,176	$ 49,819	$ 46,719	199,031	196,018	189,170
Net income available to common shareholders, diluted									199,031	196,018	189,170
Less: Earnings applicable to participating securities, basic									608	657	674
Less: Earnings applicable to participating securities, diluted									608	657	674
Earnings applicable to common shareholders									198,423	195,361	188,496
Earnings applicable to common shareholders, diluted									$ 198,423	$ 195,361	$ 188,496
Shares:
Weighted-average common shares outstanding - basic									91,367	90,968	89,899
Effect of dilutive securities:
Stock options and restricted stock (in shares)									461	524	466
Warrants (in shares)									28	41	255
Weighted Average Number of Shares Outstanding, Diluted									91,856	91,533	90,620
Earnings per common share:
Earnings per common share, Basic (in dollars per share)	$ 0.61	$ 0.54	$ 0.53	$ 0.49	$ 0.54	$ 0.54	$ 0.55	$ 0.52	$ 2.17	$ 2.15	$ 2.10
Earnings per common share, Diluted (in dollars per share)	$ 0.60	$ 0.54	$ 0.53	$ 0.49	$ 0.54	$ 0.53	$ 0.55	$ 0.51	$ 2.16	$ 2.13	$ 2.08