Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands		Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Accruals And Allowance		$ 23,661	$ 32,303
Operating Loss Carryforwards		3,317	6,358
Stock-Based Compensation		6,015	8,250
Deferred Rent		1,977	3,002
Deferred Revenue		2,740	1,957
Tax Credit Carryforwards		974	1,543
Acquired Intangibles		14,907	21,871
Depreciation And Amortization		1,185	1,160
Total Deferred Tax Assets		54,776	76,444
Depreciation And Amortization		0	0
Deferred Tax Liabilities, Other		(126)	(991)
Total Deferred Tax Liabilities		(126)	(991)
Valuation Allowance	[1]	(5,182)	(4,594)
Net Deferred Tax Assets		$ 49,468	$ 70,859

[1] Valuation allowance is presented gross. The valuation allowance net of the federal tax effect is $4.1 million and $3.0 million for the years ended December 31, 2017 and 2016, respectively.