Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of Significant Accounting Policies [Abstract]
Minimum number of days past due for nonaccrual loan status	90 days
Period of sustained repayment performance for nonperforming TDRs to be returned to performing status	6 months
Standby letters of credit expiration period	1 year
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 134,455	$ 126,012	$ 113,444
Total noninterest income out-of-scope of ASC 606	9,568	(1,250)	7,860
Total noninterest income	144,023	124,762	121,304
Insurance and Other Financial Services Revenue [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	25,006	24,345	23,532
Service Charges on Deposit Accounts [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	17,151	17,224	16,750
ATM and Debit Card Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	23,893	22,699	21,372
Retirement Plan Administration Fees [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	30,388	26,992	20,213
Trust [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	19,164	19,524	19,586
Other [Member]
Noninterest Income [Abstract]
Total noninterest income in-scope of ASC 606	$ 18,853	$ 15,228	$ 11,991