Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 32,850	$ 29,084	$ 62,708	$ 56,423
Total noninterest income out-of-scope of ASC 606	1,308	1,220	2,727	2,631
Total noninterest income	34,158	30,304	65,435	59,054
Insurance and Other Financial Services Revenue [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	5,826	5,621	12,330	12,391
Service Charges on Deposit Accounts [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	4,246	4,161	8,218	8,138
ATM and Debit Card Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	5,816	5,518	11,089	10,468
Retirement Plan Administration Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	7,296	5,437	12,635	9,609
Trust [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	5,265	5,161	10,143	9,693
Other [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 4,401	$ 3,186	$ 8,293	$ 6,124