Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Change in the allowance for unfunded commitments
Balance at beginning of period	$ 24,000
Balance at end of period	26,000	$ 24,000
Allowance for Unfunded Commitments:
Change in the allowance for unfunded commitments
Balance at beginning of period	24,336	24,400
Provision for unfunded commitments	1,500	(2,500)
Amount recorded at acquisition	0	2,436
Balance at end of period	$ 25,836	$ 24,336