Basis of Presentation (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit increase, net	$ 11,358,354		$ 13,386,589	$ 13,727,537	$ 13,512,529
Allowance for credit losses on debt securities held to maturity	1,892	$ 0	0
Allowance for credit losses on loans	$ 1,351,072	920,993	920,993	$ 966,022	$ 885,242
Allowance for credit losses on letters of credit and unfunded commitments		66,955
As Reported Under ASC 326
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for credit losses on debt securities held to maturity		1,847
Allowance for credit losses on loans		1,105,924	1,105,924
Allowance for credit losses on letters of credit and unfunded commitments		76,946
Impact of ASC 326 Adoption
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Accumulated deficit increase, net		150,200
Allowance for credit losses on debt securities held to maturity		1,847	1,847
Allowance for credit losses on loans		184,931	$ 184,931
Allowance for credit losses on letters of credit and unfunded commitments		$ 9,991