Commitments, Contingencies and Guarantees - Commitments (Details) - USD ($)	Mar. 31, 2017	Dec. 31, 2016
Financial Guarantees (Textual) [Abstract]
Potential losses from standby letters of credit	$ 0	$ 0
Undisbursed loan commitments	565,600,000	578,200,000
Probable credit losses	1,000,000	1,300,000
Financial and Performance Standby Letters of Credit
Financial Guarantees (Textual) [Abstract]
Letters of credit outstanding	118,400,000	118,900,000
Commitments to Extend Credit
Financial Guarantees (Textual) [Abstract]
Loan commitments under financial guarantee	$ 2,650,000,000	$ 2,700,000,000