Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 31,681	$ 29,498	$ 94,389	$ 85,921
Total noninterest income out-of-scope of ASC 606	1,700	1,280	4,427	3,911
Total noninterest income	33,381	30,778	98,816	89,832
Insurance and Other Financial Services Revenue [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	6,172	5,536	18,502	17,927
Service Charges on Deposit Accounts [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	4,503	4,261	12,721	12,399
ATM and Debit Card Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	5,906	5,557	16,995	16,025
Retirement Plan Administration Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	7,244	5,272	19,879	14,881
Trust [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	4,808	4,927	14,951	14,620
Other [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 3,048	$ 3,945	$ 11,341	$ 10,069