Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Rate	Dec. 31, 2012 Rate	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value	$ 86,305	$ 64,117
Corporate Bonds		500
Available-for-sale Securities, Failed Auction, Value	277	346
Foreign Currency Contracts, Liability, Fair Value Disclosure	6	268
Assets, Fair Value Disclosure	86,588	65,231
Business Acquisition, Contingent Consideration, at Fair Value	5,208
Liabilities, Fair Value Disclosure	5,208
Fair Value Inputs, Discount Rate	3.70%
Fair Value Input Discount Rate 3	6.20%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value		277	346
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)		(69)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issues, Settlements		0
Fair Value, Level 3 Transfers out, Description		0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	5,208	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	5,294
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings	138
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements	(224)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Liability, Transfers out of Level 3	0
Convertible Debt, Noncurrent	51,751	49,010
Convertible Debt, Fair Value Disclosures	59,340	51,018
Fair Value Inputs Discount Rate 2	4.20%	9.40%
Long-term Debt, Contingent Payment of Principal or Interest	0	0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value	0	0
Corporate Bonds		0
Available-for-sale Securities, Failed Auction, Value	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	0	0
Business Acquisition, Contingent Consideration, at Fair Value	0
Liabilities, Fair Value Disclosure	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value	86,305	64,117
Corporate Bonds		500
Available-for-sale Securities, Failed Auction, Value	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	6	268
Assets, Fair Value Disclosure	86,311	64,885
Business Acquisition, Contingent Consideration, at Fair Value	0
Liabilities, Fair Value Disclosure	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value	0	0
Corporate Bonds		0
Available-for-sale Securities, Failed Auction, Value	277	346
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0
Assets, Fair Value Disclosure	277	346
Business Acquisition, Contingent Consideration, at Fair Value	5,208
Liabilities, Fair Value Disclosure	$ 5,208