Commitments, Off-Balance Sheet Arrangements and Contingent Liabilities Summary of Lending Related and Other Commitments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Summary of lending-related and other commitments
Standby letters of credit Fair value	$ 3,164	$ 3,542
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	6,935,786	6,884,411
Commercial Letters Of Credit [Member]
Summary of lending-related and other commitments
Lending related commitments	11,484	9,179
Standby Letters of Credit [Member]
Summary of lending-related and other commitments
Lending related commitments	317,079	353,292
Standby letters of credit Fair value	$ 3,000	$ 4,000