Recent Accounting Pronouncements - Revenue From Contracts With Customers Beginning Balance Sheet Impact (Details) - USD ($) $ in Thousands	Mar. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	$ 74,760		$ 69,844
Prepaid expenses and other current assets	29,967		18,931
Other long-term assets	43,647		42,913
Deferred revenue	57,629		52,429
Other non-current liabilities	21,273		22,626
Accumulated deficit	(2,060,075)		$ (2,057,812)
Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net		$ 71,625
Prepaid expenses and other current assets		22,509
Other long-term assets		43,686
Deferred revenue		47,603
Other non-current liabilities		22,153
Accumulated deficit		(2,046,381)
Calculated under Revenue Guidance in Effect before Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	72,358
Prepaid expenses and other current assets	24,321
Other long-term assets	43,040
Deferred revenue	60,569
Other non-current liabilities	21,602
Accumulated deficit	(2,071,999)
Difference between Revenue Guidance in Effect before and after Topic 606 [Member] | Accounting Standards Update 2014-09 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accounts receivable, net	2,402	1,781
Prepaid expenses and other current assets	5,646	3,578
Other long-term assets	607	773
Deferred revenue	(2,940)	(4,826)
Other non-current liabilities	(329)	(473)
Accumulated deficit	$ 11,924	$ 11,431