Fair Value of Financial Instruments - Derivatives (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2013 USD ($) derivative	Sep. 30, 2012 USD ($)	Sep. 30, 2013 USD ($) derivative	Sep. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) derivative	Sep. 30, 2013 Forward Contracts EUR (€)	Sep. 30, 2013 Forward Contracts GBP (£)	Dec. 31, 2012 Forward Contracts EUR (€)
Derivatives, Fair Value [Line Items]
Derivative, number of instruments held	2		2		1
Derivative, notional amount						€ 4,200,000	£ 1,900,000	€ 10,700,000
Foreign currency contract, asset, fair value disclosure	0		0		0
Derivative instruments not designated as hedging instruments, loss	400,000	400,000	600,000	100,000
Foreign currency transaction gain, before tax	$ 300,000	$ 400,000	$ 100,000	$ 49,000