Loans (Balances Of Commercial Loan Portfolio Classes, Disaggregated By PD Grade) (Details) $ in Thousands	Sep. 30, 2017 USD ($) grade	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($) grade		Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$ 194,867	$ 197,257	$ 202,068		$ 201,557	$ 199,807	$ 210,242
Total loans collectively evaluated for impairment	19,885,440				19,192,515
Total loans individually evaluated for impairment	254,831				305,973
Purchase credit impaired loans - recorded investment	25,820				57,299
Allowance - collectively evaluated for impairment	147,928				150,777
Allowance - individually evaluated for impairment	43,804				49,614
Allowance - purchased credit impaired loans	$ 3,135		$ 700		$ 1,166
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	$ 127,888		$ 123,250
Total loans collectively evaluated for impairment	14,983,986		14,187,074
Total loans individually evaluated for impairment	34,348		51,086
Purchase credit impaired loans - recorded investment	24,525		45,450
Total commercial loans	$ 15,042,859		$ 14,283,610
Percent of loan collectively evaluated for impairment (percent)	99.00%		99.00%
Percent of loan individually evaluated for impairment (percent)	1.00%		1.00%
Percent of loan purchased-credit impaired (percent)	0.00%		0.00%
Allowance - collectively evaluated for impairment	$ 118,086		$ 118,518
Allowance - individually evaluated for impairment	7,021		4,413
Allowance - purchased credit impaired loans	2,781		319
General C I | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	10,468,700		9,710,168
Total loans individually evaluated for impairment	28,931		44,753
Purchase credit impaired loans - recorded investment	20,725		40,532
Total commercial loans	10,518,356		9,795,453
Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	1,966,155		2,045,189
Total loans individually evaluated for impairment	0		0
Purchase credit impaired loans - recorded investment	0		0
Total commercial loans	1,966,155		2,045,189
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	304,236		304,236	[1]
Total loans individually evaluated for impairment	3,097		3,209	[1]
Purchase credit impaired loans - recorded investment	0		0	[1]
Total commercial loans	307,333		307,445	[1]
Valuation allowance	$ 25,500		$ 25,500
Highest internal grade | grade	13		13
Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	$ 2,203,852		$ 2,085,619
Total loans individually evaluated for impairment	1,525		1,831
Purchase credit impaired loans - recorded investment	3,792		4,583
Total commercial loans	2,209,169		2,092,033
Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total loans collectively evaluated for impairment	41,043		41,862
Total loans individually evaluated for impairment	795		1,293
Purchase credit impaired loans - recorded investment	8		335
Total commercial loans	41,846		43,490
Commercial Loan P D Grade One | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 585,650		$ 466,257
Percent of total commercial loans (percent)	4.00%		3.00%
Loans and Leases Receivable, Allowance	$ 81		$ 77
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	583,818		465,179
Commercial Loan P D Grade One | Loans To Mortgage Companies [Member] | 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	[1]
Commercial Loan P D Grade One | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	1,832		1,078
Commercial Loan P D Grade One | Residential C R E | 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	$ 909,881		$ 803,012
Percent of total commercial loans (percent)	6.00%		6.00%
Loans and Leases Receivable, Allowance	$ 385		$ 403
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	905,992		791,183
Commercial Loan P D Grade Two | Loans To Mortgage Companies [Member] | 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	[1]
Commercial Loan P D Grade Two | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	3,777		11,742
Commercial Loan P D Grade Two | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	112		87
Commercial Loan P D Grade Three | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,300,522		$ 1,107,542
Percent of total commercial loans (percent)	9.00%		8.00%
Loans and Leases Receivable, Allowance	$ 277		$ 304
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	500,056		491,386
Commercial Loan P D Grade Three | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	643,772		462,486
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	[1]
Commercial Loan P D Grade Three | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	156,694		153,670
Commercial Loan P D Grade Three | Residential C R E | 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 | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,901,151		$ 1,532,811
Percent of total commercial loans (percent)	13.00%		11.00%
Loans and Leases Receivable, Allowance	$ 955		$ 953
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	1,026,592		978,282
Commercial Loan P D Grade Four | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	578,566		332,107
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	[1]
Commercial Loan P D Grade Four | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	295,781		222,422
Commercial Loan P D Grade Four | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	212		0
Commercial Loan P D Grade Five | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,117,757		$ 1,873,965
Percent of total commercial loans (percent)	14.00%		13.00%
Loans and Leases Receivable, Allowance	$ 7,697		$ 6,670
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	1,460,107		1,232,401
Commercial Loan P D Grade Five | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	211,846		275,209
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	[1]
Commercial Loan P D Grade Five | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	443,751		365,653
Commercial Loan P D Grade Five | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,053		702
Commercial Loan P D Grade Six | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,302,052		$ 2,502,310
Percent of total commercial loans (percent)	14.00%		17.00%
Loans and Leases Receivable, Allowance	$ 9,857		$ 10,403
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	1,519,911		1,540,519
Commercial Loan P D Grade Six | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	362,685		614,109
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	[1]
Commercial Loan P D Grade Six | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	413,342		338,344
Commercial Loan P D Grade Six | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	6,114		9,338
Commercial Loan P D Grade Seven | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 2,220,394		$ 2,228,369
Percent of total commercial loans (percent)	14.00%		16.00%
Loans and Leases Receivable, Allowance	$ 13,297		$ 14,010
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	1,705,394		1,556,117
Commercial Loan P D Grade Seven | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	60,135		317,283
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	[1]
Commercial Loan P D Grade Seven | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	446,493		352,390
Commercial Loan P D Grade Seven | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	8,372		2,579
Commercial Loan P D Grade Eight | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 1,341,553		$ 1,422,786
Percent of total commercial loans (percent)	9.00%		10.00%
Loans and Leases Receivable, Allowance	$ 20,963		$ 25,986
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	1,042,209		963,359
Commercial Loan P D Grade Eight | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	34,623		30,974
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	[1]
Commercial Loan P D Grade Eight | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	259,813		425,503
Commercial Loan P D Grade Eight | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,908		2,950
Commercial Loan P D Grade Nine | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 687,974		$ 725,767
Percent of total commercial loans (percent)	5.00%		5.00%
Loans and Leases Receivable, Allowance	$ 11,376		$ 13,857
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	556,662		611,774
Commercial Loan P D Grade Nine | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	60,954		4,299
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	[1]
Commercial Loan P D Grade Nine | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	66,082		105,277
Commercial Loan P D Grade Nine | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,276		4,417
Commercial Loan P D Grade Ten | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 433,315		$ 423,616
Percent of total commercial loans (percent)	3.00%		3.00%
Loans and Leases Receivable, Allowance	$ 8,502		$ 8,400
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	395,187		355,359
Commercial Loan P D Grade Ten | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	0		8,663
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	[1]
Commercial Loan P D Grade Ten | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	31,570		50,484
Commercial Loan P D Grade Ten | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	6,558		9,110
Commercial Loan P D Grade Eleven | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 260,435		$ 265,371
Percent of total commercial loans (percent)	2.00%		2.00%
Loans and Leases Receivable, Allowance	$ 6,730		$ 6,556
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	217,190		238,230
Commercial Loan P D Grade Eleven | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	13,548		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	[1]
Commercial Loan P D Grade Eleven | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	24,878		20,600
Commercial Loan P D Grade Eleven | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	4,819		6,541
Commercial Loan P D Grade Twelve | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 199,436		$ 190,094
Percent of total commercial loans (percent)	1.00%		1.00%
Loans and Leases Receivable, Allowance	$ 7,065		$ 6,377
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	185,929		170,531
Commercial Loan P D Grade Twelve | Loans To Mortgage Companies [Member] | 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	[1]
Commercial Loan P D Grade Twelve | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	10,798		15,395
Commercial Loan P D Grade Twelve | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	2,709		4,168
Commercial Loan P D Grade Thirteen | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 486,035		$ 432,571
Percent of total commercial loans (percent)	3.00%		3.00%
Loans and Leases Receivable, Allowance	$ 6,927		$ 4,225
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	142,729		121,276
Commercial Loan P D Grade Thirteen | Loans To Mortgage Companies [Member] | 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	304,236		304,236	[1]
Commercial Loan P D Grade Thirteen | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	38,979		6,748
Commercial Loan P D Grade Thirteen | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	91		311
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	$ 237,831		$ 212,603
Percent of total commercial loans (percent)	2.00%		1.00%
Loans and Leases Receivable, Allowance	$ 23,974		$ 20,297
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	226,924		194,572
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Loans To Mortgage Companies [Member] | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	26		59
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	[1]
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Income C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	10,062		16,313
Commercial Loan P D Grade Fourteen Fifteen Sixteen | Residential C R E | Commercial Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Commercial loan, Disaggregated by PD grade	$ 819		$ 1,659

[1] Balances as of September 30, 2017 and December 31, 2016, presented net of a $25.5 million valuation allowance. Based on the underlying structure of the notes, the highest possible internal grade is “13”.