Significant Accounting Policies Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 104,937		$ 110,718
Operating lease liabilities	113,593		119,429
Allowance for credit losses on loans and leases	328,401		157,629		$ 144,871
Reserve for Unfunded Commitments	20,286		5,106		4,523
Cumulative adjustment	2,704,577		4,313,915		4,056,442		$ 3,969,367
$ Increase (decrease)	2,704,577		4,313,915		4,056,442		3,969,367
Commercial Real Estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases	141,710		50,847		47,904
Reserve for Unfunded Commitments	15,360		534		628
Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases	150,864		73,820		63,957
Reserve for Unfunded Commitments	2,190		2,539		2,250
Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases	27,964		24,714		22,034
Reserve for Unfunded Commitments	1,661		149		160
Consumer & Other, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases	7,863		8,248		10,976
Reserve for Unfunded Commitments	1,075		1,884		1,485
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		$ 207,600
Reserve for Unfunded Commitments		8,300
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment	(932,767)		770,366		602,482		477,101
$ Increase (decrease)	$ (932,767)		770,366		602,482		477,101
Cumulative Effect, Period of Adoption, Adjusted Balance
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			207,628
Reserve for Unfunded Commitments			8,344
Cumulative Effect, Period of Adoption, Adjusted Balance | Commercial Real Estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			55,924
Reserve for Unfunded Commitments			4,564
Cumulative Effect, Period of Adoption, Adjusted Balance | Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			117,829
Reserve for Unfunded Commitments			2,052
Cumulative Effect, Period of Adoption, Adjusted Balance | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			26,813
Reserve for Unfunded Commitments			1,416
Cumulative Effect, Period of Adoption, Adjusted Balance | Consumer & Other, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			7,062
Reserve for Unfunded Commitments			312
Cumulative Effect, Period of Adoption, Adjusted Balance | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		207,628
Reserve for Unfunded Commitments		8,344
Cumulative Effect, Period of Adoption, Adjusted Balance | Accounting Standards Update 2016-13 | Commercial Real Estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		55,924
Reserve for Unfunded Commitments		4,564
Cumulative Effect, Period of Adoption, Adjusted Balance | Accounting Standards Update 2016-13 | Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		117,829
Reserve for Unfunded Commitments		2,052
Cumulative Effect, Period of Adoption, Adjusted Balance | Accounting Standards Update 2016-13 | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		26,813
Reserve for Unfunded Commitments		1,416
Cumulative Effect, Period of Adoption, Adjusted Balance | Accounting Standards Update 2016-13 | Consumer & Other, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases		7,062
Reserve for Unfunded Commitments		$ 312
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment			(40,181)	[1]	(244)	[2]	0	[3]
$ Increase (decrease)			(40,181)	[1]	(244)	[2]	0	[3]
% Increase (decrease)		33.00%
Financing Receivable, Allowance for Credit Loss and Off-Balance Sheet, Credit Loss, Liability		$ 53,237
Cumulative Effect, Period of Adoption, Adjustment | Commercial Real Estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
% Increase (decrease)		18.00%
Financing Receivable, Allowance for Credit Loss and Off-Balance Sheet, Credit Loss, Liability		$ 9,107
Cumulative Effect, Period of Adoption, Adjustment | Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
% Increase (decrease)		57.00%
Financing Receivable, Allowance for Credit Loss and Off-Balance Sheet, Credit Loss, Liability		$ 43,522
Cumulative Effect, Period of Adoption, Adjustment | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
% Increase (decrease)		14.00%
Financing Receivable, Allowance for Credit Loss and Off-Balance Sheet, Credit Loss, Liability		$ 3,366
Cumulative Effect, Period of Adoption, Adjustment | Consumer & Other, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
% Increase (decrease)		(27.00%)
Financing Receivable, Allowance for Credit Loss and Off-Balance Sheet, Credit Loss, Liability		$ (2,758)
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			49,999
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Commercial Real Estate
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			5,077
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Commercial
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			44,009
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Residential
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			2,099
Cumulative Effect, Period of Adoption, Adjustment | Accounting Standards Update 2016-13 | Consumer & Other, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on loans and leases			(1,186)
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative adjustment		(40,200)	(40,181)	[1]	(244)	[2]	(9,710)	[3]
$ Increase (decrease)		$ (40,200)	$ (40,181)	[1]	$ (244)	[2]	$ (9,710)	[3]

[1] The cumulative effect adjustment relates to the implementation of new accounting guidance on January 1, 2020, for the allowance for credit losses. Refer to Note 1 for discussion of the new accounting guidance.

[2] The cumulative effect adjustment relates to the implementation of new accounting guidance on January 1, 2019 for operating leases.

[3] The cumulative effect adjustment from retained earnings to accumulated other comprehensive income (loss) related to the implementation of new accounting guidance on January 1, 2018, for the junior subordinated debentures that the Company previously elected to fair value on a recurring basis.