Employee Benefits (Employee Benefit Plans) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Employee benefit costs	$ 15,880	$ 14,718	$ 16,112
401(k) Matching [Member]
Defined Benefit Plan Disclosure [Line Items]
401(k) matching	1,892	1,458	2,267
Deferred Bonus Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Deferred bonus plan	677	588	445
Health Benefits, Including Premiums [Member]
Defined Benefit Plan Disclosure [Line Items]
Health benefits, including premiums	$ 13,311	$ 12,672	$ 13,400