Income Tax Contingencies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Income Tax Uncertainties [Abstract]
Net interest and penalties expense	$ 424	$ 206
Accrued interest	3,155		$ 2,706
Accrued penalties	2,513		2,426
Unrecognized tax benefits related to uncertain tax positions	76,120		56,702
The amount of unrecognized tax benefits that, if recognized, would affect our effective tax rate	$ 74,671		$ 55,312