Shareholders' Equity And Earnings Per Share (Computation Of Basic And Diluted Earnings Per Common Share) (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share, Basic and Diluted, Other Disclosures [Abstract]
Net income	$ 65,626	$ 53,115	$ 188,901	$ 152,267
Less: Preferred stock dividends	2,050	3,628	7,728	10,884
Net income applicable to common shares	63,576	49,487	181,173	141,383
Add: Dividends on convertible preferred stock, if dilutive	0	1,578	1,578	4,735
Net income applicable to common shares—Diluted	$ 63,576	$ 51,065	$ 182,751	$ 146,118
Weighted average common shares outstanding (in shares)	55,796	51,679	54,292	49,763
Effect of dilutive potential common shares
Common stock equivalents (in shares)	966	938	988	822
Convertible preferred stock, if dilutive (in shares)	0	3,109	1,317	3,109
Total dilutive potential common shares (in shares)	966	4,047	2,305	3,931
Weighted average common shares and effect of dilutive potential common shares (in shares)	56,762	55,726	56,597	53,694
Net income per common share-Basic (usd per share)	$ 1.14	$ 0.96	$ 3.34	$ 2.84
Net income per common share-Diluted (usd per share)	$ 1.12	$ 0.92	$ 3.23	$ 2.72