Goodwill and Acquired Intangible Assets, Net - Acquired Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Acquired intangible assets, net:
Cost	$ 95,180	$ 95,180
Accumulated amortization	46,022	35,207
Total expected future amortization expense	49,158	59,973
Developed technology
Acquired intangible assets, net:
Cost	19,096	19,096
Accumulated amortization	19,062	18,628
Total expected future amortization expense	$ 34	$ 468
Weighted- average remaining useful life	2 months 12 days	9 months 18 days
Customer relationships
Acquired intangible assets, net:
Cost	$ 74,484	$ 74,484
Accumulated amortization	25,360	14,979
Total expected future amortization expense	$ 49,124	$ 59,505
Weighted- average remaining useful life	5 years 2 months 12 days	6 years 2 months 12 days
Tradenames
Acquired intangible assets, net:
Cost	$ 1,600	$ 1,600
Accumulated amortization	1,600	1,600
Total expected future amortization expense	$ 0	$ 0