Basis of Presentation and Summary of Significant Accounting Policies - Disaggregation of Revenues (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenues
Revenue	$ 314,109	$ 305,280	$ 307,722	$ 365,451	$ 393,586	$ 373,545	$ 390,849	$ 404,357	$ 1,292,562	$ 1,562,337	$ 1,586,222
United States
Disaggregation of Revenues
Revenue									1,057,006	1,286,678	1,347,516
EMEA
Disaggregation of Revenues
Revenue									213,418	248,466	211,314
Other
Disaggregation of Revenues
Revenue									22,138	27,193	27,392
ITPS
Disaggregation of Revenues
Revenue	243,537	234,365	243,029	284,112	306,665	292,607	309,840	325,172	1,005,043	1,234,284	1,273,647
ITPS | United States
Disaggregation of Revenues
Revenue									769,487	958,625	1,034,941
ITPS | EMEA
Disaggregation of Revenues
Revenue									213,418	248,466	211,314
ITPS | Other
Disaggregation of Revenues
Revenue									22,138	27,193	27,392
HS
Disaggregation of Revenues
Revenue	51,623	54,209	49,166	64,049	69,806	62,132	63,440	61,343	219,047	256,721	228,015
HS | United States
Disaggregation of Revenues
Revenue									219,047	256,721	228,015
LLPS
Disaggregation of Revenues
Revenue	$ 18,949	$ 16,706	$ 15,527	$ 17,290	$ 17,115	$ 18,806	$ 17,569	$ 17,842	68,472	71,332	84,560
LLPS | United States
Disaggregation of Revenues
Revenue									$ 68,472	$ 71,332	$ 84,560