Commitments, Guarantees, and Contingent Liabilities (Details) - USD ($) $ in Thousands		Mar. 31, 2019	Dec. 31, 2018
Other Commitments [Line Items]
Letters of credit		$ 120,028	$ 112,728
Commitments to extend credit
Other Commitments [Line Items]
Commercial, industrial, and agricultural		1,686,990	1,729,286
Commercial real estate		302,263	296,882
Home equity		578,969	570,553
Other commitments	[1]	244,222	244,917
Total commitments to extend credit		$ 2,812,444	$ 2,841,638

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