Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits, period increase (decrease)			$ (59)	$ (3,280)
Income tax expense	$ 2,222	$ (302)	$ 4,348	$ 567
United States
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent			21.00%