Related Party Transactions (Transaction with Related Parties) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Prepaid expenses and other current assets	$ 14,652		$ 15,357
Accrued expenses	48,854		55,507
Financing derivatives	19,200		21,587
Senior secured convertible notes	186,115		184,075
Investor
Related Party Transaction [Line Items]
Accounts receivable, net	2,249		2,698
Prepaid expenses and other current assets	1,061		1,180
Accounts payable	3,336		2,510
Accrued expenses	6,353		6,902
WPP \| Investor
Related Party Transaction [Line Items]
Revenues	3,211	$ 3,845
Accounts receivable, net	2,249		2,542
Prepaid expenses and other current assets	1,061		1,180
Accounts payable	3,336		2,510
Accrued expenses	233		716
Contract liability	2,314		1,361
WPP \| Investor \| Cost of revenues
Related Party Transaction [Line Items]
Expenses	2,375	2,095
WPP \| Investor \| Selling and marketing
Related Party Transaction [Line Items]
Expenses	2	3
WPP \| Investor \| General and administrative
Related Party Transaction [Line Items]
Expenses	142	$ 40
Starboard Value LP \| Investor
Related Party Transaction [Line Items]
Accrued expenses	6,120		6,120
Financing derivatives	19,200		21,587
Senior secured convertible notes	$ 186,115		$ 184,075

Amount for accounts payable to related parties. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

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