Commitments, Guarantees, and Contingent Liabilities (Details) - Contractual or Notional Amounts of Financial Instruments - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
Commitments to extend credit:
Letters of credit		$ 112,728	$ 128,801
Commitments to extend credit
Commitments to extend credit:
Commercial, industrial, and agricultural		1,729,286	1,729,426
Commercial real estate		296,882	377,551
Home equity		570,553	514,973
Other commitments	[1]	244,917	244,222
Total commitments to extend credit		$ 2,841,638	$ 2,866,172

[1] Other commitments includes installment and overdraft protection program commitments.