Long-Term Debt (Narrative) (Details)	12 Months Ended							12 Months Ended								3 Months Ended	12 Months Ended				12 Months Ended
	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Dec. 31, 2013 Unsecured Euro-denominated term loan facility USD ($)	Dec. 31, 2013 Unsecured Euro-denominated term loan facility EUR (€)	Dec. 31, 2013 Credit agreement USD ($)	Dec. 31, 2013 Revolving credit facility due November 2014 USD ($)	Dec. 31, 2013 Revolving credit facility due in August 2018 USD ($)	Dec. 31, 2012 Revolving credit facility due in August 2018	Dec. 31, 2013 Revolving credit facility due in August 2018 LIBOR	Dec. 31, 2013 Revolving credit facility due July 2016 USD ($)	Dec. 31, 2013 Unsecured term loan due in August 2018 USD ($)	Dec. 31, 2013 Unsecured term loan due in August 2018 LIBOR	Dec. 31, 2013 Unsecured term loan due in December 2019 USD ($)	Dec. 31, 2013 Unsecured term loan due in December 2019 LIBOR	Sep. 30, 2013 Unsecured senior notes due 2015 USD ($)	Dec. 31, 2012 Unsecured senior notes due 2015 USD ($)	Dec. 31, 2012 Unsecured 5.625% senior notes due 2014 USD ($)	Dec. 31, 2013 Unsecured 5.625% senior notes due 2014 EUR (€)	Dec. 31, 2012 Unsecured 5.625% senior notes due 2014 EUR (€)	Dec. 31, 2013 Unsecured term loans guaranteed by an export credit agency Minimum	Dec. 31, 2013 Unsecured term loans guaranteed by an export credit agency Maximum	Dec. 31, 2013 Unsecured term loans guaranteed by an export credit agency Up-front Payment Arrangement Minimum	Dec. 31, 2013 Unsecured term loans guaranteed by an export credit agency Up-front Payment Arrangement Maximum
Long-Term Debt
Maximum borrowing capacity under credit agreement				$ 502,900,000	€ 365,000,000							$ 380,000,000		$ 65,000,000
Long term debt, due date (year)								2018	2018									2014	2014
Margin on floating rate base (as a percent)										1.75%			2.12%		2.12%
Borrowing capacity						2,000,000,000.0	525,000,000.0	850,000,000			1,100,000,000.0
Facility fee								3.675%	3.675%			0.37%		0.37%
Increase in capacity								300,000,000			20,000,000
Maximum cash purchase through extended tender offer																21,000,000.0		328,000,000		255,000,000.0
Long term debt, principal amount								850,000,000											745,000,000	1,000,000,000.0
Interest rate on debt instrument (as a percent)																11.875%		5.625%	5.625%
Premium, fees and related cost of repurchase of unsecured debt																24,900,000		344,600,000
Loss on early extinguishment of debt	$ 4,206,000	$ 7,501,000														$ 4,200,000	$ 7,500,000
Credit agency fees, percentage of outstanding loan balance																					0.88%	1.48%
Credit agency fees, percentage of maximum loan amount payable																							2.30%	2.37%