Income Tax (Component of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Deferred tax assets:
Net operating loss carryforwards	$ 7,975	$ 10,008
Research and development tax credit carryforwards	9,652	8,185
Stock-based compensation	6,723	5,529
Accrued expenses	4,629	4,108
AMT tax credit carryforwards	1,790	1,727
Allowance for doubtful accounts	1,660	1,264
Other	4,613	4,275
Total deferred tax assets	37,042	35,096
Valuation allowance	(19,576)	(6,447)
Deferred tax assets, net of valuation allowance	17,466	28,649
Deferred tax liabilities:
Depreciation and amortization	(16,952)	(28,649)
Total deferred tax liabilities	(16,952)	(28,649)
Net deferred tax assets, net of valuation allowance	$ 514	$ 0