Commitments and Contingencies Commitments (Details) $ in Thousands	Mar. 31, 2020 USD ($)
Lending related commitments [Line Items]
Unused Commitments to Extend Credit	$ 4,201,458
Loan Origination Commitments [Member]
Lending related commitments [Line Items]
Unused Commitments to Extend Credit	344,419
Loan Purchase Commitments [Member]
Lending related commitments [Line Items]
Unused Commitments to Extend Credit	791,759
Unused lines of Credit [Member]
Lending related commitments [Line Items]
Unused Commitments to Extend Credit	2,979,737
Standby Letters of Credit [Member]
Lending related commitments [Line Items]
Unused Commitments to Extend Credit	$ 85,543