Significant Accounting Policies - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenues
Revenue	$ 307,722	$ 390,849	$ 673,173	$ 795,206
United States
Disaggregation of Revenues
Revenue	255,468	320,235	560,196	650,920
EMEA
Disaggregation of Revenues
Revenue	47,084	63,823	100,990	130,501
Other
Disaggregation of Revenues
Revenue	5,170	6,791	11,987	13,785
ITPS
Disaggregation of Revenues
Revenue	243,029	309,840	527,140	635,012
ITPS | United States
Disaggregation of Revenues
Revenue	190,775	239,226	414,163	490,726
ITPS | EMEA
Disaggregation of Revenues
Revenue	47,084	63,823	100,990	130,501
ITPS | Other
Disaggregation of Revenues
Revenue	5,170	6,791	11,987	13,785
HS
Disaggregation of Revenues
Revenue	49,166	63,440	113,216	124,783
HS | United States
Disaggregation of Revenues
Revenue	49,166	63,440	113,216	124,783
LLPS
Disaggregation of Revenues
Revenue	15,527	17,569	32,817	35,411
LLPS | United States
Disaggregation of Revenues
Revenue	$ 15,527	$ 17,569	$ 32,817	$ 35,411