Restructuring Costs - Summary of Pre-tax Costs Incurred (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost And Reserve [Line Items]
Restructuring costs	[1]	$ 3,525	$ 1,785	$ 25,256
Employee Severance
Restructuring Cost And Reserve [Line Items]
Restructuring costs		73	498	5,834
Contract Termination And Other Costs
Restructuring Cost And Reserve [Line Items]
Restructuring costs		631	1,287	1,453
Stock Based Compensation
Restructuring Cost And Reserve [Line Items]
Restructuring costs		0	0	2,074
Impairment of Property and Equipment
Restructuring Cost And Reserve [Line Items]
Restructuring costs		2,821	0	0
Derecognition of Goodwill And Intangibles Assets
Restructuring Cost And Reserve [Line Items]
Restructuring costs		$ 0	$ 0	$ 15,895

[1] Includes stock-based compensation, net of amounts capitalized as follows: Year Ended December 31, (in thousands) 2018 2017 2016 Cost of revenue $8,931 $2,503 $4,114 Research and development 48,739 9,918 5,756 Sales and marketing 19,046 8,069 8,712 General and administrative 55,054 14,496 12,301 Restructuring — — 2,074 Stock-based compensation, net of amounts capitalized $131,770 $34,986 $32,957