Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	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	$ 64,117	$ 70,525
Available-for-sale Securities, Failed Auction, Value	346	363
Available-for-sale Securities, Fair Value Disclosure	64,963	70,888
Foreign Currency Contracts, Liability, Fair Value Disclosure	268	99
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	268	99
Financial Instruments, Owned, at Fair Value	65,231	70,987
Fair Value Inputs, Discount Rate	2.50%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	346	363
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	8
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issues, Settlements	(25)
Fair Value, Level 3 Transfers out, Description	0
Convertible Debt, Noncurrent	49,010	46,524
Convertible Debt, Fair Value Disclosures	51,018	46,524
Fair Value Inputs Discount Rate 2	9.40%
Long-term Debt, Contingent Payment of Principal or Interest	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
Available-for-sale Securities, Failed Auction, Value	0	0
Available-for-sale Securities, Fair Value Disclosure	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure		99
Derivative Financial Instruments, Liabilities, Fair Value Disclosure		99
Financial Instruments, Owned, at Fair Value	268	99
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	64,117	70,525
Available-for-sale Securities, Failed Auction, Value	0	0
Available-for-sale Securities, Fair Value Disclosure	64,617	70,525
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Financial Instruments, Owned, at Fair Value	64,617	70,525
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
Available-for-sale Securities, Failed Auction, Value		363
Available-for-sale Securities, Fair Value Disclosure	346	363
Foreign Currency Contracts, Liability, Fair Value Disclosure	0	0
Derivative Financial Instruments, Liabilities, Fair Value Disclosure	0	0
Financial Instruments, Owned, at Fair Value	$ 346	$ 363