Fair Value Measurements - (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2014 Rate	Dec. 31, 2013 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	$ 127,618	$ 86,305
Available-for-sale Securities, Failed Auction, Value	295	277
Foreign Currency Contracts, Liability, Fair Value Disclosure	21
Foreign Currency Contract, Asset, Fair Value Disclosure		6
Assets, Fair Value Disclosure	127,913	86,588
Business Combination, Contingent Consideration, Liability	(5,283)	5,208
Liabilities, Fair Value Disclosure	5,304
Fair Value Input Discount Rate	3.30%
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value	295	277
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Other Comprehensive Income (Loss)	18
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases, Sales, Issues, Settlements	0
Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Sales, Issues, Settlements	0
Fair Value, Level 3 Transfers out, Description	0
Fair Value, Measurement with Unobservable Inputs Reconciliations, Recurring Basis, Liability Value	5,283	5,208
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Gain (Loss) Included in Other Comprehensive Income (Loss)	0
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Purchases	(75)
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Liability, Settlements	0
Convertible Debt	52,486	51,751
Long-term Debt, Fair Value	60,390	59,340
Fair Value Inputs Discount Rate 2	3.50%	4.20%
Long-term Debt, Contingent Payment of Principal or Interest	0	0
Fair Value Inputs Discount Rate 3	5.70%
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
Available-for-sale Securities, Failed Auction, Value	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	0
Foreign Currency Contract, Asset, Fair Value Disclosure		0
Assets, Fair Value Disclosure	0	0
Business Combination, Contingent Consideration, Liability	0	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	127,618	86,305
Available-for-sale Securities, Failed Auction, Value	0	0
Foreign Currency Contracts, Liability, Fair Value Disclosure	21
Foreign Currency Contract, Asset, Fair Value Disclosure		6
Assets, Fair Value Disclosure	127,618	86,311
Business Combination, Contingent Consideration, Liability	0	0
Liabilities, Fair Value Disclosure	(21)
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	295	277
Foreign Currency Contracts, Liability, Fair Value Disclosure	0
Foreign Currency Contract, Asset, Fair Value Disclosure		0
Assets, Fair Value Disclosure	295	277
Business Combination, Contingent Consideration, Liability	(5,283)	5,208
Liabilities, Fair Value Disclosure	$ 5,283