Non Purchased Loans - Narrative (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) loan	Mar. 31, 2017 USD ($) loan	Dec. 31, 2017 USD ($)
Loans and Allowance for Loan Losses (Additional Textual) [Abstract]
Allowance for loan losses attributable to restructured loans	$ 46,401,000		$ 46,211,000
Non purchased loans and leases
Loans and Allowance for Loan Losses (Additional Textual) [Abstract]
Mortgage and commercial loans discontinued past due period	90 days
Consumer and other retail loans charged-off past due period	120 days
Troubled debt restructured	$ 5,216,000	$ 156,000	$ 5,588,000
Nonperforming loans charged-off past due period	90 days
Number of restructured loans | loan	4	1
Restructured loans discontinued past due period	90 days	90 days
Remaining availability under commitments to lend additional funds on restructured loans	$ 20,000	$ 142,000
Non purchased loans and leases | Nonaccruing Loans
Loans and Allowance for Loan Losses (Additional Textual) [Abstract]
Outstanding balance of restructured loans	571,000	57,000
Non purchased loans and leases | Restructured Loans
Loans and Allowance for Loan Losses (Additional Textual) [Abstract]
Outstanding balance of restructured loans	2,570,000	6,086,000
Allowance for loan losses attributable to restructured loans	$ 92,000	$ 241,000