Long-Term Debt and Other Borrowed Funds (Details) - USD ($)	Jan. 08, 2018	Jan. 29, 2015	Jan. 10, 2008	Dec. 31, 2017	Nov. 16, 2017	Dec. 31, 2016	Dec. 31, 2014
Debt Instrument
Long-term debt and capital lease obligations				$ 13,100,000		$ 28,000,000
Fiscal Year Maturities of Long-term Debt
2018				100,000
2019				100,000
2020				100,000
2021				100,000
2022				5,100,000
Thereafter				7,600,000
Long-term debt and capital lease obligations				13,100,000		28,000,000
Advances from FHLB				0		0
Other borrowings				20,009,000		6,000
Parent Company
Debt Instrument
Long-term debt				0		$ 20,000,000
Subordinated term loan | Subordinated Term Loan, 6.81% | Parent Company
Debt Instrument
Stated interest rate						6.81%
Long-term debt				$ 0		$ 20,000,000
Fiscal Year Maturities of Long-term Debt
Repayments of Unsecured Debt			$ 20,000,000
Subordinated term loan | Note Payable, 6.24% | Parent Company
Debt Instrument
Stated interest rate							6.24%
Capital lease obligations | Capital Lease Obligation, 8.00% | Subsidiaries
Debt Instrument
Stated interest rate				8.00%
Capital Lease Obligations				$ 1,400,000		1,500,000
Notes payable | Note Payable, 6.24% | Subsidiaries
Debt Instrument
Stated interest rate				6.24%
Long-term debt				$ 1,600,000		1,500,000
Notes payable | Note Payable, 2.28% | Subsidiaries
Debt Instrument
Stated interest rate				2.28%
Long-term debt				$ 5,000,000		5,000,000
Notes payable | Note Payable, 1.00% | Subsidiaries
Debt Instrument
Stated interest rate				1.00%	1.00%
Long-term debt				$ 5,100,000	$ 5,100,000	$ 0
Federal Home Loan Bank | Notes Payable to FHLB | Subsidiaries
Fiscal Year Maturities of Long-term Debt
FHLB, advances, maximum amount available				$ 1,313,300,000
Secured Debt
Debt Instrument
Stated interest rate		2.28%
Fiscal Year Maturities of Long-term Debt
Ownership percentage in subsidiary				99.90%
Repayments of Unsecured Debt		$ 5,000,000
Federal Funds Purchased
Fiscal Year Maturities of Long-term Debt
Line of credit facility, maximum borrowing capacity				$ 185,000,000
Federal Reserve Bank Advances
Fiscal Year Maturities of Long-term Debt
Line of credit facility, maximum borrowing capacity				$ 464,800,000
Subsequent Event | Subordinated term loan | Subordinated Term Loan, 6.81%
Debt Instrument
Stated interest rate	6.81%
Fiscal Year Maturities of Long-term Debt
Repayments of Unsecured Debt	$ 20,000,000
Subsequent Event | Subordinated term loan | Subordinated Term Loan, 6.81% | Parent Company
Debt Instrument
Stated interest rate	6.81%
Fiscal Year Maturities of Long-term Debt
Repayments of Unsecured Debt	$ 20,000,000