Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Change in the allowance for unfunded commitments
Balance at beginning of period	$ 24,000
Balance at end of period	25,000	$ 24,000
Allowance for Unfunded Commitments:
Change in the allowance for unfunded commitments
Balance at beginning of period	24,400	25,400
Provision for unfunded commitments	(1,500)	(1,000)
Amount recorded at acquisition	2,436	0
Balance at end of period	$ 25,336	$ 24,400