Derivative Instruments (Details)	3 Months Ended			3 Months Ended				3 Months Ended
	Mar. 31, 2013 USD ($)	Mar. 31, 2012 USD ($)	Dec. 31, 2012 USD ($)	Mar. 31, 2013 [InterestRateSwapMember] USD ($)	Mar. 31, 2012 [InterestRateSwapMember] USD ($)	Mar. 31, 2013 [InterestRateSwapPayFixedRateReceiveFloatingRateMember] USD ($)	Mar. 31, 2013 [InterestRateSwapPayFixedRateReceiveFloatingRateLowerFixedInterestRatesMember] USD ($)	Mar. 31, 2013 [ForeignExchangeContractMember] USD ($)	Mar. 31, 2013 [ForeignExchangeContractMember] EUR (€)	Mar. 31, 2013 [InterestRateSwapAmountsDueToFromCounterpartiesForTerminationOfAgreementsMember] [NondesignatedMember] USD ($)
Derivative Instruments
Notional Amount of Derivative Contracts				$ 765,800,000
Notional Amount of Derivative Contracts						1,100,200,000
Notional Amount of Derivative Contracts						334,400,000
Weighted average fixed leg (Pay) interest rate (as a percent)				1.68%
Weighted Average Remaining Term				6 years 2 months 12 days
Notional amount of derivative contracts terminated						516,800,000
Notional Amount of Derivative Contracts							550,000,000
Fair value of derivative instruments (assets)	3,382,000		1,904,000							2,400,000
Fair value of derivative instruments (liabilities)	35,396,000		34,633,000							16,700,000
Amortization of net loss on terminated derivative instruments designated as cash flow hedges	783,000	800,000		800,000	800,000
Unamortized pre-tax balance in accumulated other comprehensive loss attributable to interest rate swap contracts				13,300,000
Unamortized pre-tax balance in accumulated other comprehensive loss attributable to interest rate swap which is expected to be amortized over the next 12 months				8,700,000
Foreign Currency Rate Swaps
Payments in Euros under foreign currency rate swap agreements									2,200,000
Receipts in U.S. dollars under foreign currency rate swap agreements								$ 3,400,000