Basis of Presentation Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL	$ 282,358	$ 272,920		$ 166,209	$ 172,797	$ 176,941	$ 169,410
Change in retained earnings	(1,099,684)			(1,079,391)
Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL		$ 0	$ 58,348
Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL			58,300
Change in retained earnings			43,800
Increase in deferred tax assets			12,400
Residential Mortgage
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL for certain OBS credit exposure	$ 1,100			$ 3,200
Residential Mortgage | Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL for certain OBS credit exposure			(2,100)
Residential Mortgage | Accounting Standards Update 2016-13 | Cumulative Effect, Period of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase in ACL for certain OBS credit exposure			$ (2,100)