Derivative Financial Instruments Derivative Financial Instruments Narrative (Details) (USD $)								3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Minimum [Member]	Mar. 31, 2013 Maximum [Member]	Mar. 31, 2013 contracts	Mar. 31, 2013 Forward Contracts [Member]	Mar. 31, 2013 Net Investment Hedging [Member]	Mar. 31, 2013 Secured Debt [Member]	Dec. 31, 2012 Secured Debt [Member]
Net unrealized loss on hedging instruments	$ (16,142,000)	$ (16,069,000)	$ (14,380,000)	$ (14,380,000)					$ (14,400,000)
Number of Interest Rate Derivatives Held							6
Notional Amount of Interest Rate Derivatives							200,000,000
Long-term Debt										398,750,000	417,500,000
Pay fixed interest rate in interst rate swap							1.00%
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net							(963,000)
Number of foreign exchange forward contracts entered into YTD								118
Notional amount of foreign currency forward contracts					$ 258,000	$ 11,000,000