Loans - Textual (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018 USD ($) executive	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($) segment tenant class_of_loan executive	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of portfolio segment (in segment) | segment			2
Number of classes of loans (in class of loan) | class_of_loan			6
Number of minimum tenants under lease of non-owner occupied commercial real estate (in tenant) | tenant			1
Minimum value of loan that requires regional loan committee approval	$ 3,000		$ 3,000
Maximum value of loan that requires regional loan committee approval	7,000		7,000
Total troubled debt restructurings	73,596		73,596		$ 77,888
Residential mortgage loans in process of foreclosure	3,200		3,200		4,200
Commitment to lend additional funds to borrowers whose terms have been modified in TDRs	2,500		2,500		2,000
Loans held-for-sale, at fair value	46,849		46,849		52,133
Proceeds from sales of loans	202,135	$ 199,944	392,570	$ 391,475
Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	25,330		25,330		29,106
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	48,266		48,266		48,782
Consumer loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	17,896		17,896		19,046
Consumer loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	3,791		3,791		4,748
Consumer loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	14,105		14,105		14,298
Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	55,700		55,700		58,842
Commercial loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	21,539		21,539		24,358
Commercial loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	34,161		$ 34,161		$ 34,484
Land development loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum period for payment of loan			12 months
Residential mortgage
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period for loan secured under real estate residential security			15 years
Loan-to-value ratio at the time of origination			80.00%
Commercial | Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Minimum value of loan requires group loan authority approval	1,250		$ 1,250
Maximum value of loan requires senior officer approval	$ 3,000		$ 3,000
Number of bank executives and senior officers with credit decision limits similar to group loan authorities (in executive) | executive	6		6
Maximum value of loan requires executive and senior officer approval	$ 8,000		$ 8,000
Minimum value of loan requires group loan authority approval	$ 7,000		$ 7,000