Loans - Textual (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) executive	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) class_of_loan segment tenant executive	Sep. 30, 2017 USD ($)	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	71,086		71,086		$ 77,888
Residential mortgage loans in process of foreclosure	5,400		5,400		4,200
Commitment to lend additional funds to borrowers whose terms have been modified in TDRs	2,900		2,900		2,000
Loans held-for-sale, at fair value	93,736		93,736		52,133
Proceeds from sales of loans	177,200	$ 210,200	569,768	$ 601,694
Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	28,061		28,061		29,106
Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	43,025		43,025		48,782
Consumer loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	17,612		17,612		19,046
Consumer loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	3,970		3,970		4,748
Consumer loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	13,642		13,642		14,298
Commercial loan portfolio
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	53,474		53,474		58,842
Commercial loan portfolio | Nonperforming
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	24,091		24,091		24,358
Commercial loan portfolio | Performing
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total troubled debt restructurings	29,383		$ 29,383		$ 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