Revenues Revenue Recognition by Segment (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		$ 246,077	$ 288,247	$ 290,084
Noninterest Income, Outside of Scope of Topic 606		267,979	92,577	65,484
Total noninterest income		514,056	380,824	355,568
Wealth management fees(a)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606	[1]	84,957	83,467	82,562
Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		56,307	63,135	66,075
Card-based fees(b)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		38,605	39,912	39,810
Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		45,245	89,104	89,511
Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		20,963	12,629	12,126
Corporate and Commercial Specialty [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		105,678	97,899	98,251
Noninterest Income, Outside of Scope of Topic 606		43,778	38,198	33,820
Corporate and Commercial Specialty [Member] | Wealth management fees(a)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		83,570	80,719	79,685
Corporate and Commercial Specialty [Member] | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		16,903	13,342	15,424
Corporate and Commercial Specialty [Member] | Card-based fees(b)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		1,534	1,827	1,796
Corporate and Commercial Specialty [Member] | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		208	364	349
Corporate and Commercial Specialty [Member] | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		3,462	1,647	997
Community, Consumer and Business [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		141,775	188,666	190,225
Noninterest Income, Outside of Scope of Topic 606		43,962	35,046	22,486
Community, Consumer and Business [Member] | Wealth management fees(a)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		1,387	2,838	2,655
Community, Consumer and Business [Member] | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		39,371	49,744	50,582
Community, Consumer and Business [Member] | Card-based fees(b)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		36,937	37,895	37,977
Community, Consumer and Business [Member] | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		45,027	88,727	89,123
Community, Consumer and Business [Member] | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		19,053	9,462	9,887
Risk Management and Shared Services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		(1,375)	1,532	1,609
Noninterest Income, Outside of Scope of Topic 606		180,237	19,483	9,176
Risk Management and Shared Services [Member] | Wealth management fees(a)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		0	(90)	222
Risk Management and Shared Services [Member] | Service charges and deposit account fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		33	49	69
Risk Management and Shared Services [Member] | Card-based fees(b)
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		134	190	37
Risk Management and Shared Services [Member] | Insurance commissions and fees
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		10	13	39
Risk Management and Shared Services [Member] | Other revenue
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Noninterest Income In Scope of Topic 606		(1,552)	1,370	1,242
Risk Management and Shared Serivies [Member] | ABRC [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Gain (Loss) on Disposition of Assets for Financial Service Operations		163,000
Operating Segments [Member] | Corporate and Commercial Specialty [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income		149,456	136,097	132,071
Operating Segments [Member] | Community, Consumer and Business [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income		185,737	223,712	212,711
Operating Segments [Member] | Risk Management and Shared Services [Member]
Revenue Recognition, Multiple-deliverable Arrangements [Line Items]
Total noninterest income		$ 178,862	$ 21,015	$ 10,785

[1] (a) Includes trust, asset management, brokerage, and annuity fees.