Segment Information - Financial Information by Major Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 321,334	$ 362,488	$ 402,279	$ 285,594	$ 296,916	$ 358,163	$ 363,677	$ 277,428	$ 1,371,695	$ 1,296,184	$ 1,306,965
Long-lived assets:
Total long-lived assets	546,020				376,757				546,020	376,757	353,083
Domestic Plans
Revenue:
Total revenue									925,140	894,442	913,210
Long-lived assets:
Total long-lived assets	205,399				182,140				205,399	182,140	180,345
EMEA
Revenue:
Total revenue									235,436	218,247	209,824
Long-lived assets:
Total long-lived assets	63,582				48,553				63,582	48,553	43,630
Canada
Revenue:
Total revenue									211,119	183,495	183,931
Long-lived assets:
Total long-lived assets	$ 277,039				$ 146,064				$ 277,039	$ 146,064	$ 129,108