Derivative Financial Instruments (Details)	9 Months Ended		3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2012 GBP (£)	Sep. 30, 2012 Not Designated as Hedging Instrument [Member] Interest rate swaps [Member] Interest expense [Member] USD ($)	Sep. 30, 2011 Not Designated as Hedging Instrument [Member] Interest rate swaps [Member] Interest expense [Member] USD ($)	Sep. 30, 2012 Not Designated as Hedging Instrument [Member] Interest rate swaps [Member] Interest expense [Member] USD ($)	Sep. 30, 2011 Not Designated as Hedging Instrument [Member] Interest rate swaps [Member] Interest expense [Member] USD ($)	Sep. 30, 2012 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Gain (loss) on foreign currency [Member] USD ($)	Sep. 30, 2011 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Gain (loss) on foreign currency [Member] USD ($)	Sep. 30, 2012 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Gain (loss) on foreign currency [Member] USD ($)	Sep. 30, 2011 Not Designated as Hedging Instrument [Member] Foreign exchange contracts [Member] Gain (loss) on foreign currency [Member] USD ($)
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain (loss) recognized in income on derivative			$ 12,000	$ 37,000	$ 68,000	$ 230,000	$ (733,000)	$ (138,000)	$ (590,000)	$ (181,000)
Notional amount of foreign currency contracts	$ 67,000,000	£ 7,100,000
Foreign currency contracts, maximum maturity period	1 year	1 year