Commitments, Off-Balance Sheet Arrangements, and Legal Proceedings (Summary of Lending Related and Other Commitments) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Commitments to extend credit, excluding commitments to originate residential mortgage loans held for sale [Member]
Summary of lending-related and other commitments
Lending related commitments	$ 7,315,642	$ 7,402,518
Commercial Letters Of Credit [Member]
Summary of lending-related and other commitments
Lending related commitments	7,782	9,945
Standby Letters of Credit [Member]
Summary of lending-related and other commitments
Lending related commitments	278,740	296,508
Standby letters of credit, fair value	$ 3,000	$ 3,000