Goodwill and Identifiable Intangible Assets - Schedule of Identifiable Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 102,823	$ 103,513
Accumulated Amortization	91,711	87,153
Net Carrying Amount	$ 11,112	16,360
Remaining Weighted-Average Amortization Periods in Years	5 years 10 months 24 days
Core Deposit Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 87,674	87,674
Accumulated Amortization	78,353	73,494
Net Carrying Amount	$ 9,321	14,180
Remaining Weighted-Average Amortization Periods in Years	4 years 4 months 24 days
Insurance Intangibles [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 13,824	13,824
Accumulated Amortization	12,348	12,026
Net Carrying Amount	$ 1,476	1,798
Remaining Weighted-Average Amortization Periods in Years	15 years 6 months
Banking Charters [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,325	1,325
Accumulated Amortization	1,010	943
Net Carrying Amount	$ 315	382
Remaining Weighted-Average Amortization Periods in Years	4 years 8 months 12 days
Borrower Relationship Intangible [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 0	690
Accumulated Amortization	0	690
Net Carrying Amount	$ 0	$ 0