Commitments, Off-Balance Sheet Arrangements, and Contingent Liabilities, Summary of Lending Related and Other Commitments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Schedule of lending-related and other commitments [Line Items]
Lending related commitments, fair value	$ 0	$ 0
Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale
Summary of lending-related and other commitments
Lending related commitments	8,027,187	8,131,131
Commercial Letters Of Credit
Summary of lending-related and other commitments
Lending related commitments	11,886	7,923
Standby Letters of Credit
Summary of lending-related and other commitments
Lending related commitments	235,361	259,632
Standby letters of credit, fair value	$ 2,000	$ 3,000