Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Contingency [Line Items]
Domestic	$ 34,678,000	$ 25,794,000	$ 16,177,000
Foreign	351,000	1,281,000	(88,000)
Income before provision for income taxes	35,029,000	27,075,000	16,089,000
Current:
Federal	8,218,000	7,181,000	4,285,000
State	1,621,000	1,006,000	896,000
Foreign	447,000	154,000	(70,000)
Total current	10,286,000	8,341,000	5,111,000
Deferred:
Federal	1,287,000	2,169,000	1,116,000
State	(263,000)	651,000	(527,000)
Foreign	(260,000)	(264,000)	0
Total deferred	764,000	2,556,000	589,000
Provision for income taxes	11,050,000	10,897,000	5,700,000
Income Tax Reconciliation:
U.S. federal tax provision at statutory rate	12,260,000	9,476,000	5,631,000
State taxes	883,000	1,077,000	240,000
Non-deductible expenses	297,000	530,000	481,000
Acquisition costs	0	431,000	0
Share-based compensation expense	407,000	403,000	443,000
Research tax credits	(1,430,000)	0	(755,000)
Domestic production deduction	(816,000)	(601,000)	(271,000)
Other	(551,000)	(419,000)	(69,000)
Provision for income taxes	11,050,000	10,897,000	5,700,000
Components of Deferred Tax Assets and Liabilities:
Deferred Tax Assets, Tax Credit Carryforwards	3,160,000	2,990,000
Deferred Tax Assets, Inventory related items	2,947,000	2,900,000
Deferred Tax Assets, Deferred revenue	11,074,000	11,497,000
Deferred Tax Assets, Stock compensation	7,447,000	9,331,000
Deferred Tax Assets, Loss carry forwards	64,000	53,000
Deferred Tax Assets, Other net	5,000	69,000
Deferred Tax Assets, Gross	24,697,000	26,840,000
Deferred Tax Assets, Valuation Allowance	(39,000)	(39,000)
Deferred Tax Assets, Net of Valuation Allowance	24,658,000	26,801,000
Deferred Tax Liabilities, Reserves and accruals	(353,000)	(573,000)
Deferred Tax Liabilities, Depreciation and amortization	(38,681,000)	(39,840,000)
Deferred Tax Liabilities, Gross	(39,034,000)	(40,413,000)
Deferred Tax Liabilities, Net	14,376,000	13,612,000
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Unrecognized Tax Benefits	6,915,000	5,796,000	5,431,000
Increases related to tax positions taken during a prior period	406,000	43,000
Increases related to tax positions related to MTS		1,066,000
Decreases related to tax positions taken during the prior period	(79,000)		(88,000)
Increases related to tax positions taken during the current period	764,000	422,000	453,000
Decreases related to settlements		(33,000)
Decreases related to expiration of statute of limitations	(32,000)	(379,000)
Unrecognized Tax Benefits	7,974,000	6,915,000	5,796,000
Tax effected amounts of gross unrealized net operating loss and business tax credit carry forwards excluded under ASC 718	2,600,000
Undistributed Earnings of Foreign Subsidiaries	2,800,000
Unrecognized tax benefits that would affect tax expense	7,000,000
Deferred Tax Liability Not Recognized, Amount of Unrecognized Deferred Tax Liability, Undistributed Earnings of Foreign Subsidiaries	1,100,000
State and Local Jurisdiction [Member]
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Operating Loss Carryforwards	2,200,000
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward [Member]
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Tax Credit Carryforward, Amount	7,200,000
Internal Revenue Service (IRS) [Member] | Research Tax Credit Carryforward [Member]
Reconciliation of Unrecognized Tax Benefits [Roll Forward]
Tax Credit Carryforward, Amount	$ 1,500,000