Long-term Debt (Senior Notes) (Narrative) (Details) (USD $)	3 Months Ended							3 Months Ended		1 Months Ended	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 Senior Notes [Member] 5.375% Senior Notes [Member]	Mar. 31, 2013 Senior Notes [Member] 5.375% Senior Notes [Member]	Feb. 28, 2013 Senior Notes [Member] 5.375% Senior Notes [Member]	Mar. 31, 2014 Senior Notes [Member] 5.375% Senior Notes [Member] Level 2 Securities [Member]	Dec. 31, 2013 Senior Notes [Member] 5.375% Senior Notes [Member] Level 2 Securities [Member]	Mar. 31, 2013 Senior Notes [Member] 8.50% Senior Notes [Member]	Dec. 31, 2013 Senior Notes [Member] 8.50% Senior Notes [Member]	Feb. 28, 2014 Senior Notes [Member] 5.750% Senior Notes [Member]	Mar. 31, 2014 Senior Notes [Member] 5.750% Senior Notes [Member]	Mar. 31, 2014 Senior Notes [Member] 5.750% Senior Notes [Member] Level 2 Securities [Member]	Mar. 31, 2014 Senior Notes [Member] 5.750% Senior Notes [Member] Other non-current assets [Member]
Debt Instrument [Line Items]
Face amount					$ 500,000,000				$ 200,000,000.0	$ 400,000,000.0
Interest rate			5.375%		5.375%			8.50%		5.75%
Proceeds from debt, net of issuance costs										392,900,000
Unamortized debt issuance expense													7,100,000
Accrued debt issuance costs											400,000
Redemption prices, percent of outstanding principal			101.00%								101.00%
Repayments	0	219,362,000		224,500,000
Make-whole premium								19,400,000
Interest payable								5,100,000
Loss on extinguishment of debt	0	(25,129,000)						25,100,000
Write off of unamortized deferred financing costs								4,200,000
Senior notes, fair value						$ 525,000,000	$ 506,300,000					$ 414,000,000