Revenue Disaggregated Revenue by Geography (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 307,471	$ 327,169	$ 950,685	$ 1,059,662
EMEA [Member]
Disaggregation of Revenue [Line Items]
Revenues	31,474	30,759	96,830	104,150
Other foreign countries [Member]
Disaggregation of Revenue [Line Items]
Revenues	53,398	51,569	156,353	154,278
Foreign [Member]
Disaggregation of Revenue [Line Items]
Revenues	84,872	82,328	253,183	258,428
UNITED STATES
Disaggregation of Revenue [Line Items]
Revenues	$ 222,599	$ 244,841	$ 697,502	$ 801,234