Loans And Allowance For Credit Losses (Summary Of Changes In The Allowance For Credit Losses) (Details) - USD ($) $ 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	Dec. 31, 2016	Dec. 31, 2015
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				$ 606,048				$ 604,663	$ 606,048	$ 604,663
Provision for loan losses	$ (2,687)	$ 18,825	$ 34,492	42,145	$ 22,701	$ 18,262	$ 566	(1,494)	92,775	40,035	$ (98,082)
Adjustment for FDIC-supported loans									0	5
Gross loan and lease charge-offs									(197,365)	(138,929)
Recoveries									66,064	100,274
Net loan and lease charge-offs									(131,301)	(38,655)
Balance at end of period	567,522				606,048				567,522	606,048	604,663
Balance at beginning of period				74,838				81,076	74,838	81,076
Provision charged (credited) to earnings									(9,927)	(6,238)
Balance at end of period	64,911				74,838				64,911	74,838	81,076
Allowance for loan losses	567,522			606,048	606,048			604,663	606,048	604,663	604,663	$ 567,522	$ 606,048
Reserve for unfunded lending commitments	64,911			74,838	74,838			81,076	74,838	81,076	81,076	64,911	74,838
Total allowance for credit losses												632,433	680,886
Commercial [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				454,277				412,514	454,277	412,514
Provision for loan losses									92,796	96,995
Adjustment for FDIC-supported loans									0	(57)
Gross loan and lease charge-offs									(169,260)	(110,437)
Recoveries									42,907	55,262
Net loan and lease charge-offs									(126,353)	(55,175)
Balance at end of period	420,720				454,277				420,720	454,277	412,514
Balance at beginning of period				57,696				58,931	57,696	58,931
Provision charged (credited) to earnings									(3,464)	(1,235)
Balance at end of period	54,232				57,696				54,232	57,696	58,931
Allowance for loan losses	420,720			454,277	454,277			412,514	454,277	412,514	412,514	420,720	454,277
Reserve for unfunded lending commitments	54,232			57,696	57,696			58,931	57,696	58,931	58,931	54,232	57,696
Total allowance for credit losses												474,952	511,973
Commercial Real Estate [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				113,992				145,009	113,992	145,009
Provision for loan losses									217	(51,777)
Adjustment for FDIC-supported loans									0	57
Gross loan and lease charge-offs									(12,146)	(14,194)
Recoveries									13,864	34,897
Net loan and lease charge-offs									1,718	20,703
Balance at end of period	115,927				113,992				115,927	113,992	145,009
Balance at beginning of period				16,526				21,517	16,526	21,517
Provision charged (credited) to earnings									(5,847)	(4,991)
Balance at end of period	10,679				16,526				10,679	16,526	21,517
Allowance for loan losses	115,927			113,992	113,992			145,009	113,992	145,009	145,009	115,927	113,992
Reserve for unfunded lending commitments	10,679			16,526	16,526			21,517	16,526	21,517	21,517	10,679	16,526
Total allowance for credit losses												126,606	130,518
Consumer [Member]
Allowance for Credit Losses [Roll Forward]
Balance at beginning of period				37,779				47,140	37,779	47,140
Provision for loan losses									(238)	(5,183)
Adjustment for FDIC-supported loans									0	5
Gross loan and lease charge-offs									(15,959)	(14,298)
Recoveries									9,293	10,115
Net loan and lease charge-offs									(6,666)	(4,183)
Balance at end of period	30,875				37,779				30,875	37,779	47,140
Balance at beginning of period				616				628	616	628
Provision charged (credited) to earnings									(616)	(12)
Balance at end of period	0				616				0	616	628
Allowance for loan losses	30,875			37,779	37,779			47,140	37,779	47,140	47,140	30,875	37,779
Reserve for unfunded lending commitments	$ 0			$ 616	$ 616			$ 628	$ 616	$ 628	$ 628	0	616
Total allowance for credit losses												$ 30,875	$ 38,395