Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2018
Operating Loss Carryforwards [Line Items]
Additions for tax positions related to current year	$ 29	$ 2,762	$ 59	$ 3,280
Effective income tax rate	7.10%		7.26%
Income tax expense	$ 2,222	$ (302)	$ 4,348	567
Income Tax Expense (Benefit), before discrete items	$ (2,193)		$ (4,289)
Effective Income Tax Rate Reconciliation, Excluding Discrete Items, Percent	7.00%		7.20%
Unrecognized Tax Benefits	$ 9,203		$ 9,203
Unrecognized tax benefits, period increase (decrease)			$ (59)	$ (3,280)
United States
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%
Scenario, Forecast
Operating Loss Carryforwards [Line Items]
Effective income tax rate					7.17%