Income Taxes - Unrecognized tax benefits activity (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Balance-beginning of year	$ 28,673	$ 30,164
Acquisitions	0	0
Increases based on tax positions of the current year	393	2,065
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities	(10,457)	0
Decreases due to lapse of statute	(5,118)	(392)
Increases based on tax positions of the prior years	156	1,217
Decreases based on tax positions of the prior years	(1,065)	(4,908)
Currency translation adjustments	(2)	(527)
Balance-end of year	$ 12,580	$ 28,673