Income Taxes Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating Loss Carryforwards [Line Items]
Unrecognized tax benefits, period increase (decrease)	$ (30)	$ (518)
Income tax expense	$ 2,126	$ 869
United States
Operating Loss Carryforwards [Line Items]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%