Summary of Significant Accounting Policies Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2020	Mar. 31, 2020		Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)		$ 2,296,176	[1]		$ 2,380,867
Held to maturity allowance for credit loss		61		$ 61
Allowance for Loan Losses					201,371
Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for Loan Losses				131,147
Allowance for Loan Losses [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for Loan Losses		$ 337,793			$ 201,371
Accounting Standards Update 2016-13
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Retained Earnings (Accumulated Deficit)				98,000
Deferred Income Tax Assets, Net				33,000
Accounting Standards Update 2016-13 | Forecast
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Reasonable and Supportable Period 2016-13	2 years
Accounting Standards Update 2016-13 | Allowance for Loan Losses [Member] | Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for Loan Losses				112,000
Accounting Standards Update 2016-13 | Allowance for Loans Losses and Unfunded Commitments [Member] | Cumulative Effect, Period Of Adoption, Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for Loan Losses				$ 131,000

[1] (b) At January 1, 2020, the adoption of ASU 2016-13 resulted in an increase to the allowance for loan losses of $112 million and an increase to the allowance for unfunded commitments of $19 million for a total increase to the ACLL of $131 million. A corresponding after tax decrease to common equity of $98 million was recorded along with a deferred tax asset of $33 million, included in accrued expenses and other liabilities. Prior periods were unadjusted due to the modified retrospective application of ASU 2016-13.