Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized tax benefits, beginning of period	$ 56,702	$ 57,626	$ 54,880
Gross increase to positions in prior years	22,943	3,367	1,164
Gross decrease to positions in prior years	(24,949)	(5,559)	(612)
Gross increases to current period tax positions	63,869	6,453	5,071
Audit settlements	(2,977)	(5,169)	(1,116)
Decrease related to lapsing of statute of limitations	(1,368)	(3,445)	(860)
Effect of change in exchange rates	(1,662)	3,429	(901)
Unrecognized tax benefits, end of period	112,558	56,702	57,626
The amount of unrecognized tax benefits that, if recognized, would affect our effective tax rate	111,224	55,312	56,411
Net interest and penalties expense (benefit)	(990)	(543)	$ 193
Accrued interest	2,127	2,706
Accrued penalties	$ 1,758	$ 2,426