Other Operating Costs (Benefit) (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Other Expense [Line Items]
Office consolidation, net	$ 242	$ 542	$ 2,766
Expected cash payments relating to office closure obligations	900
One time cost relating to legal matter	1,600
Office Space Reductions [Member]
Other Income and Other Expense [Line Items]
Office consolidation, net			2,600
Restructured real estate	$ 1,680	$ 3,060	$ 3,083