Derivative Instruments (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Derivative Instruments (Textual) [Abstract]
Open forward foreign currency exchange contract not designated as a hedge	$ 18,099,000	$ 16,258,000
Derivative foreign currency exchange contracts settlement date	1 month
Open forward foreign currency exchange contract designated as a cash flow hedge	1,177,000	1,197,000
Open interest rate contracts designated as a cash flow hedge	$ 2,693,000	$ 2,969,000