Debt (Senior Notes and Senior Credit Facilities Narrative) (Details) (USD $)	6 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended	6 Months Ended	12 Months Ended	1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended			1 Months Ended	6 Months Ended
	Jun. 30, 2014	Nov. 30, 2012 Senior Unsecured Notes Due 2022 [Member]	Jun. 30, 2014 Senior Unsecured Notes Due 2022 [Member]	Dec. 31, 2013 Senior Unsecured Notes Due 2022 [Member]	May 31, 2011 Senior Unsecured Notes Due 2021 [Member]	Jun. 30, 2014 Senior Unsecured Notes Due 2021 [Member]	Dec. 31, 2013 Senior Unsecured Notes Due 2021 [Member]	Sep. 30, 2010 Senior Unsecured Notes Due 2018 [Member]	Jun. 30, 2014 Senior Unsecured Notes Due 2018 [Member]	Dec. 31, 2013 Senior Unsecured Notes Due 2018 [Member]	Sep. 30, 2013 Revolving Credit Facility [Member]	Jun. 30, 2014 Revolving Credit Facility [Member]	Sep. 16, 2013 Revolving Credit Facility [Member]	Apr. 30, 2013 Credit-Linked Revolving Facility [Member]	Jun. 30, 2014 Credit-Linked Revolving Facility [Member]	Sep. 30, 2013 Credit-Linked Revolving Facility [Member]	Jun. 30, 2014 Credit-Linked Revolving Facility [Member] London Interbank Offered Rate (LIBOR) [Member]	Sep. 30, 2013 Term C-2 Loan Facility [Member]	Jun. 30, 2014 Term C-2 Loan Facility [Member]	Jun. 30, 2014 Term C-2 Loan Facility [Member] London Interbank Offered Rate (LIBOR) [Member]	Jun. 30, 2014 Term C-2 Loan Facility [Member] European Interbank Offered Rate (EURIBOR) [Member]	Jun. 30, 2014 Amended Credit Agreement [Member]
Debt Instrument [Line Items]
Senior notes		$ 500,000,000			$ 400,000,000			$ 600,000,000
Interest rate, stated percentage		4.625%	4.625%	4.625%	5.875%	5.875%	5.875%	6.625%	6.625%	6.625%
Year of maturity		Nov. 15, 2022	Nov. 15, 2022	Nov. 15, 2022	Jun. 15, 2021	Jun. 15, 2021	Jun. 15, 2021	Oct. 15, 2018	Oct. 15, 2018	Oct. 15, 2018
Borrowing capacity													600,000,000			81,000,000
Cross default covenant to other debt																						$ 40,000,000
Credit facility, expiration date											Oct. 31, 2015			Mar. 28, 2014	Mar. 28, 2014			Oct. 31, 2016	Oct. 31, 2016
Estimated margin																	2.50%			2.00%	2.00%
Amortization rate of initial principal amount per annum payable quarterly	1.00%
Line of credit facility, unused capacity, commitment fee percentage												0.25%