Fair Value Measurements - (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2013	Jun. 30, 2013 Rate	Dec. 31, 2012 Rate
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Instruments, Owned, State and Municipal Government Obligations, at Fair Value	$ 90,231	$ 90,231	$ 64,117
Corporate Bonds	500	500	500
Available-for-sale Securities, Failed Auction, Value	302	302	346
Available-for-sale Securities, Fair Value Disclosure	91,033	91,033	64,963
Business Acquisition, Contingent Consideration, at Fair Value	6,198	6,198
Liabilities, Fair Value Disclosure	6,198	6,198
Foreign Currency Contracts, Liability, Fair Value Disclosure	13	13	268
Assets, Fair Value Disclosure	91,046	91,046	65,231
Fair Value Input Discount Rate		3.20%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	(5,896)	(5,896)	346
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	(44)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issues, Settlements	(6,198)
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales, Issues, Settlements	0
Fair Value, Level 3 Transfers out, Description	0
Convertible Debt	50,347	50,347	49,010
Long-term Debt, Fair Value	52,242	52,242	51,018
Fair Value Inputs Discount Rate 2		9.40%	9.40%
Fair Value Inputs Discount Rate 2		1.20%
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	0
Corporate Bonds	0	0	0
Available-for-sale Securities, Failed Auction, Value	0	0	0
Business Acquisition, Contingent Consideration, at Fair Value	0	0
Liabilities, Fair Value Disclosure	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure			0
Assets, Fair Value Disclosure	0	0	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	90,231	90,231	64,117
Corporate Bonds	500	500	500
Available-for-sale Securities, Failed Auction, Value	0	0	0
Business Acquisition, Contingent Consideration, at Fair Value	0	0
Liabilities, Fair Value Disclosure	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	13	13	268
Assets, Fair Value Disclosure	90,744	90,744	64,885
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	0
Corporate Bonds	0	0	0
Available-for-sale Securities, Failed Auction, Value	302	302	346
Business Acquisition, Contingent Consideration, at Fair Value	6,198	6,198
Liabilities, Fair Value Disclosure	6,198	6,198
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0	0
Assets, Fair Value Disclosure	$ 302	$ 302	$ 346