Long-Term Debt (Parenthetical) (Details)	12 Months Ended																																																		12 Months Ended
	Dec. 31, 2013 $1.1 billion unsecured revolving credit facility, LIBOR plus 1.75%, currently 1.91% and a facility fee of 0.3675%, due 2016 USD ($)	Dec. 31, 2012 $1.1 billion unsecured revolving credit facility, LIBOR plus 1.75%, currently 1.91% and a facility fee of 0.3675%, due 2016	Dec. 31, 2013 Revolving credit facility due in August 2018 USD ($)	Dec. 31, 2012 Revolving credit facility due in August 2018	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Lower Limit	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Lower Limit	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 1	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 1	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 2	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 2	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 3	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 3	Dec. 31, 2013 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 4	Dec. 31, 2012 Unsecured senior notes and senior debentures, 5.25% to 11.88%, due 2015, 2016, 2018, 2022 and 2027 Upper Limit Period 4	Dec. 31, 2013 €745 million unsecured senior notes, 5.63%, due 2014 EUR (€)	Dec. 31, 2012 €745 million unsecured senior notes, 5.63%, due 2014 EUR (€)	Dec. 31, 2013 $570 million unsecured term loan, 4.02%, due through 2013 USD ($)	Dec. 31, 2012 $570 million unsecured term loan, 4.02%, due through 2013	Dec. 31, 2013 $589 million unsecured term loan, 4.47%, due through 2014 USD ($)	Dec. 31, 2012 $589 million unsecured term loan, 4.47%, due through 2014	Dec. 31, 2013 $530 million unsecured term loan, LIBOR plus 0.51%, currently 0.87%, due through 2015 USD ($)	Dec. 31, 2012 $530 million unsecured term loan, LIBOR plus 0.51%, currently 0.87%, due through 2015	Dec. 31, 2013 $519 million unsecured term loan, LIBOR plus 0.45%, currently 0.81%, due through 2020 USD ($)	Dec. 31, 2012 $519 million unsecured term loan, LIBOR plus 0.45%, currently 0.81%, due through 2020	Dec. 31, 2013 $420 million unsecured term loan, 5.41%, due through 2021 USD ($)	Dec. 31, 2012 $420 million unsecured term loan, 5.41%, due through 2021	Dec. 31, 2013 $420 million unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2021 USD ($)	Dec. 31, 2012 $420 million unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2021	Dec. 31, 2013 €159.4 million unsecured term loan, EURIBOR plus 1.58%, currently 1.92%, due through 2021 EUR (€)	Dec. 31, 2012 €159.4 million unsecured term loan, EURIBOR plus 1.58%, currently 1.92%, due through 2021	Dec. 31, 2013 $524.5 million unsecured term loan, LIBOR plus 0.50%, currently 0.90%, due through 2021 USD ($)	Dec. 31, 2012 $524.5 million unsecured term loan, LIBOR plus 0.50%, currently 0.90%, due through 2021	Dec. 31, 2013 $566.1 million unsecured term loan, LIBOR plus 0.37%, currently 0.74%, due through 2022 USD ($)	Dec. 31, 2012 $566.1 million unsecured term loan, LIBOR plus 0.37%, currently 0.74%, due through 2022	Dec. 31, 2013 $1.1 billion unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2022 USD ($)	Dec. 31, 2012 $1.1 billion unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2022	Dec. 31, 2013 $632.0 million unsecured term loan, LIBOR plus 0.40%, currently 0.80%, due through 2023 USD ($)	Dec. 31, 2012 $632.0 million unsecured term loan, LIBOR plus 0.40%, currently 0.80%, due through 2023	Dec. 31, 2013 $673.5 million unsecured term loan, LIBOR plus 0.40%, currently 0.77%, due through 2024 USD ($)	Dec. 31, 2012 $673.5 million unsecured term loan, LIBOR plus 0.40%, currently 0.77%, due through 2024	Dec. 31, 2013 $290.0 million unsecured term loan, LIBOR plus 2.5%, currently 2.67%, due 2016 USD ($)	Dec. 31, 2012 $290.0 million unsecured term loan, LIBOR plus 2.5%, currently 2.67%, due 2016	Dec. 31, 2013 €365 million unsecured term loan, EURIBOR plus 3.0%, currently 3.23%, due 2017 EUR (€)	Dec. 31, 2012 €365 million unsecured term loan, EURIBOR plus 3.0%, currently 3.23%, due 2017	Dec. 31, 2013 $7.3 million unsecured term loan, LIBOR plus 2.5%, currently 2.93%, due through 2023 USD ($)	Dec. 31, 2012 $7.3 million unsecured term loan, LIBOR plus 2.5%, currently 2.93%, due through 2023	Dec. 31, 2013 $30.3 million unsecured term loan, LIBOR plus 3.75%, currently 3.99%, due through 2021 USD ($)	Dec. 31, 2012 $30.3 million unsecured term loan, LIBOR plus 3.75%, currently 3.99%, due through 2021	Dec. 31, 2013 LIBOR $1.1 billion unsecured revolving credit facility, LIBOR plus 1.75%, currently 1.91% and a facility fee of 0.3675%, due 2016	Dec. 31, 2013 LIBOR Revolving credit facility due in August 2018	Dec. 31, 2013 LIBOR $530 million unsecured term loan, LIBOR plus 0.51%, currently 0.87%, due through 2015	Dec. 31, 2013 LIBOR $519 million unsecured term loan, LIBOR plus 0.45%, currently 0.81%, due through 2020	Dec. 31, 2013 LIBOR $420 million unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2021	Dec. 31, 2013 LIBOR $524.5 million unsecured term loan, LIBOR plus 0.50%, currently 0.90%, due through 2021	Dec. 31, 2013 LIBOR $566.1 million unsecured term loan, LIBOR plus 0.37%, currently 0.74%, due through 2022	Dec. 31, 2013 LIBOR $1.1 billion unsecured term loan, LIBOR plus 2.10%, currently 2.46%, due through 2022	Dec. 31, 2013 LIBOR $632.0 million unsecured term loan, LIBOR plus 0.40%, currently 0.80%, due through 2023	Dec. 31, 2013 LIBOR $673.5 million unsecured term loan, LIBOR plus 0.40%, currently 0.77%, due through 2024	Dec. 31, 2013 LIBOR $290.0 million unsecured term loan, LIBOR plus 2.5%, currently 2.67%, due 2016	Dec. 31, 2013 LIBOR $7.3 million unsecured term loan, LIBOR plus 2.5%, currently 2.93%, due through 2023	Dec. 31, 2013 LIBOR $30.3 million unsecured term loan, LIBOR plus 3.75%, currently 3.99%, due through 2021	Dec. 31, 2013 EURIBOR €159.4 million unsecured term loan, EURIBOR plus 1.58%, currently 1.92%, due through 2021	Dec. 31, 2013 EURIBOR €365 million unsecured term loan, EURIBOR plus 3.0%, currently 3.23%, due 2017
Long-Term Debt
Long term debt, principal amount	$ 1,100,000,000		$ 850,000,000														€ 745,000,000	€ 1,000,000,000.0	$ 570,000,000		$ 589,000,000		$ 530,000,000		$ 519,000,000		$ 420,000,000		$ 420,000,000		€ 159,400,000.0		$ 524,500,000.0		$ 566,100,000.0		$ 1,100,000,000		$ 632,000,000		$ 673,500,000.0		$ 290,000,000		€ 365,000,000		$ 7,300,000.0		$ 30,300,000.0
Long term debt, stated interest rate (as a percent)																	5.625%	5.625%	4.02%		4.47%						5.41%
Long term debt, current interest rate (as a percent)	1.91%		1.92%																				0.87%		0.81%				2.46%		1.92%		0.90%		0.74%		2.46%		0.80%		0.77%		2.67%		3.23%		2.93%		3.99%
Long term debt, facility fee	0.3675%	0.3675%	3.675%	3.675%
Margin on floating rate base (as a percent)																																																			1.75%	1.75%	0.51%	0.45%	2.10%	0.50%	0.37%	2.10%	0.40%	0.40%	2.50%	2.50%	3.75%	1.58%	3.00%
Long term debt, due date (year)	2016	2016	2018	2018			2015	2015	2016	2016	2018	2018	2022	2022	2027	2027	2014	2014	2013	2013	2014	2014	2015	2015	2020	2020	2021	2021	2021	2021	2021	2021	2021	2021	2022	2022	2022	2022	2023	2023	2024	2024	2016	2016	2017	2017	2023	2023	2021	2021
Long term debt, minimum stated interest rate					5.25%	5.25%
Long term debt, maximum stated interest rate					11.88%	11.88%