Loans, Changes in the Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Change in the Allowance for Unfunded Commitments
Balance at beginning of period	$ 25,000
Balance at end of period	24,000	$ 25,000
Allowance for Unfunded Commitments
Change in the Allowance for Unfunded Commitments
Balance at beginning of period	25,400	24,400	$ 24,900
Provision for Other Credit Losses	(1,000)	1,000	(500)
Balance at end of period	$ 24,400	$ 25,400	$ 24,400