Loans (Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade) (Details) $ in Thousands	Mar. 31, 2018 USD ($) grade	Dec. 31, 2017 USD ($) grade	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$ 187,194	$ 189,555	$ 201,968	$ 202,068
Total loans collectively evaluated for impairment	26,847,384		18,762,625
Total loans individually evaluated for impairment	249,602		283,550
Purchased credit-impaired loans	152,807		43,899
Allowance - collectively evaluated for impairment	145,365		157,056
Allowance - individually evaluated for impairment	39,274		44,322
Allowance - purchased credit-impaired loans	$ 2,555	$ 3,200	$ 590
Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percent of total commercial loans (percent)	100.00%	100.00%
Loans and Leases Receivable, Allowance	$ 129,295	$ 126,638
Total loans collectively evaluated for impairment	19,907,115	20,091,018
Total loans individually evaluated for impairment	42,835	45,431
Purchased credit-impaired loans	112,793	135,519
Total commercial loans	$ 20,062,743	$ 20,271,968
Percent of loan collectively evaluated for impairment (percent)	99.00%	99.00%
Percent of loan individually evaluated for impairment (percent)	0.00%	0.00%
Percent of loan purchased-credit impaired (percent)	1.00%	1.00%
Allowance - collectively evaluated for impairment	$ 122,472	$ 117,649
Allowance - individually evaluated for impairment	4,555	6,176
Allowance - purchased credit-impaired loans	2,268	2,813
General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	13,617,494	13,511,033
Total loans individually evaluated for impairment	37,732	39,957
Purchased credit-impaired loans	81,655	99,407
Total commercial loans	13,736,881	13,650,397
Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	1,784,553	2,099,961
Total loans individually evaluated for impairment	0	0
Purchased credit-impaired loans	0	0
Total commercial loans	1,784,553	2,099,961
TRUPS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Valuation allowance	25,500	25,500
TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	303,848	303,848
Total loans individually evaluated for impairment	3,026	3,067
Purchased credit-impaired loans	0	0
Total commercial loans	306,874	306,915
Valuation allowance	$ 25,500	$ 25,500
Highest internal grade | grade	13	13
Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	$ 4,099,003	$ 4,077,337
Total loans individually evaluated for impairment	1,582	1,612
Purchased credit-impaired loans	26,840	31,615
Total commercial loans	4,127,425	4,110,564
Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	102,217	98,839
Total loans individually evaluated for impairment	495	795
Purchased credit-impaired loans	4,298	4,497
Total commercial loans	107,010	104,131
Commercial Loan P D Grade One | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 547,706	$ 538,744
Percent of total commercial loans (percent)	3.00%	3.00%
Loans and Leases Receivable, Allowance	$ 65	$ 70
Commercial Loan P D Grade One | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	545,484	536,244
Commercial Loan P D Grade One | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade One | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade One | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,222	2,500
Commercial Loan P D Grade One | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Two | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 845,904	$ 879,502
Percent of total commercial loans (percent)	4.00%	4.00%
Loans and Leases Receivable, Allowance	$ 270	$ 339
Commercial Loan P D Grade Two | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	834,975	877,635
Commercial Loan P D Grade Two | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Two | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Two | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	10,885	1,798
Commercial Loan P D Grade Two | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	44	69
Commercial Loan P D Grade Three | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,292,151	$ 1,445,319
Percent of total commercial loans (percent)	6.00%	7.00%
Loans and Leases Receivable, Allowance	$ 247	$ 272
Commercial Loan P D Grade Three | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	622,790	582,224
Commercial Loan P D Grade Three | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	447,007	652,982
Commercial Loan P D Grade Three | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Three | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	222,179	210,073
Commercial Loan P D Grade Three | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	175	40
Commercial Loan P D Grade Four | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,737,153	$ 1,898,712
Percent of total commercial loans (percent)	9.00%	9.00%
Loans and Leases Receivable, Allowance	$ 732	$ 854
Commercial Loan P D Grade Four | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	879,672	959,581
Commercial Loan P D Grade Four | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	523,519	629,432
Commercial Loan P D Grade Four | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Four | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	333,962	309,699
Commercial Loan P D Grade Four | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Five | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,396,115	$ 2,208,347
Percent of total commercial loans (percent)	12.00%	11.00%
Loans and Leases Receivable, Allowance	$ 8,100	$ 7,355
Commercial Loan P D Grade Five | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,650,506	1,461,632
Commercial Loan P D Grade Five | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	320,248	328,477
Commercial Loan P D Grade Five | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Five | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	424,334	415,764
Commercial Loan P D Grade Five | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,027	2,474
Commercial Loan P D Grade Six | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,439,947	$ 2,463,301
Percent of total commercial loans (percent)	12.00%	12.00%
Loans and Leases Receivable, Allowance	$ 10,254	$ 10,495
Commercial Loan P D Grade Six | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,627,095	1,668,247
Commercial Loan P D Grade Six | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	340,287	335,169
Commercial Loan P D Grade Six | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Six | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	469,570	456,706
Commercial Loan P D Grade Six | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,995	3,179
Commercial Loan P D Grade Seven | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,826,207	$ 2,869,430
Percent of total commercial loans (percent)	14.00%	14.00%
Loans and Leases Receivable, Allowance	$ 13,839	$ 13,490
Commercial Loan P D Grade Seven | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,302,232	2,257,400
Commercial Loan P D Grade Seven | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	57,103	47,720
Commercial Loan P D Grade Seven | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Seven | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	457,280	554,590
Commercial Loan P D Grade Seven | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	9,592	9,720
Commercial Loan P D Grade Eight | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,336,045	$ 1,376,652
Percent of total commercial loans (percent)	7.00%	7.00%
Loans and Leases Receivable, Allowance	$ 21,037	$ 21,831
Commercial Loan P D Grade Eight | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,057,573	1,092,994
Commercial Loan P D Grade Eight | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	26,144	35,266
Commercial Loan P D Grade Eight | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Eight | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	246,274	241,938
Commercial Loan P D Grade Eight | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	6,054	6,454
Commercial Loan P D Grade Nine | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 4,451,128	$ 4,396,420
Percent of total commercial loans (percent)	22.00%	22.00%
Loans and Leases Receivable, Allowance	$ 13,946	$ 9,804
Commercial Loan P D Grade Nine | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,614,872	2,633,854
Commercial Loan P D Grade Nine | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	70,245	70,915
Commercial Loan P D Grade Nine | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Nine | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,698,234	1,630,176
Commercial Loan P D Grade Nine | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	67,777	61,475
Commercial Loan P D Grade Ten | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 386,685	$ 421,424
Percent of total commercial loans (percent)	2.00%	2.00%
Loans and Leases Receivable, Allowance	$ 7,644	$ 8,808
Commercial Loan P D Grade Ten | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	341,763	373,537
Commercial Loan P D Grade Ten | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Ten | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Ten | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	39,370	43,297
Commercial Loan P D Grade Ten | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	5,552	4,590
Commercial Loan P D Grade Eleven | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 282,181	$ 261,103
Percent of total commercial loans (percent)	1.00%	1.00%
Loans and Leases Receivable, Allowance	$ 6,803	$ 6,784
Commercial Loan P D Grade Eleven | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	250,720	226,382
Commercial Loan P D Grade Eleven | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Eleven | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Eleven | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	30,871	31,785
Commercial Loan P D Grade Eleven | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	590	2,936
Commercial Loan P D Grade Twelve | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 533,211	$ 573,366
Percent of total commercial loans (percent)	3.00%	3.00%
Loans and Leases Receivable, Allowance	$ 6,817	$ 5,882
Commercial Loan P D Grade Twelve | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	407,146	409,838
Commercial Loan P D Grade Twelve | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Twelve | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Twelve | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	118,478	156,717
Commercial Loan P D Grade Twelve | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	7,587	6,811
Commercial Loan P D Grade Thirteen | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 573,219	$ 522,436
Percent of total commercial loans (percent)	3.00%	3.00%
Loans and Leases Receivable, Allowance	$ 7,683	$ 7,265
Commercial Loan P D Grade Thirteen | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	233,421	202,613
Commercial Loan P D Grade Thirteen | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Thirteen | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	303,848	303,848
Commercial Loan P D Grade Thirteen | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	35,938	15,707
Commercial Loan P D Grade Thirteen | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	12	268
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 259,463	$ 236,262
Percent of total commercial loans (percent)	1.00%	1.00%
Loans and Leases Receivable, Allowance	$ 25,035	$ 24,400
Commercial Loan P D Grade Fourteen Fifteen Sixteen | General C&I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	249,245	228,852
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Loans To Mortgage Companies | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Fourteen Fifteen Sixteen | TRUPS | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0	0
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Income CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	9,406	6,587
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Residential CRE | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 812	$ 823