Debt (Senior Notes) (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended			0 Months Ended		6 Months Ended		0 Months Ended	6 Months Ended		0 Months Ended	6 Months Ended		0 Months Ended		0 Months Ended	6 Months Ended		0 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Apr. 13, 2012 8.25% Senior Notes [Member]	Jul. 24, 2009 8.25% Senior Notes [Member]	Jun. 30, 2014 8.25% Senior Notes [Member]	Dec. 31, 2013 8.25% Senior Notes [Member]	Jul. 13, 2012 5.75% Senior Notes [Member]	Jun. 30, 2014 5.75% Senior Notes [Member]	Dec. 31, 2013 5.75% Senior Notes [Member]	Sep. 28, 2012 5.625% Senior Notes [Member]	Jun. 30, 2014 5.625% Senior Notes [Member]	Dec. 31, 2013 5.625% Senior Notes [Member]	Jul. 01, 2014 4.875% Senior Notes [Member]	Jun. 30, 2014 4.875% Senior Notes [Member]	Apr. 29, 2009 4.0% Convertible Senior Notes [Member]	Jun. 30, 2014 4.0% Convertible Senior Notes [Member]	Dec. 31, 2013 4.0% Convertible Senior Notes [Member]	Jul. 24, 2009 Senior Notes [Member]	Aug. 15, 2014 Scenario, Forecast [Member] 8.25% Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes							$ 375,000,000			$ 800,000,000			$ 500,000,000			$ 750,000,000
Debt instrument, maturity date							Aug. 15, 2019	Aug. 15, 2019		Jul. 15, 2020	Jul. 15, 2020		Oct. 01, 2019	Oct. 01, 2019		Jul. 15, 2022		Oct. 01, 2014	Oct. 01, 2014
Debt instrument, interest rate, stated percentage							8.25%	8.25%		5.75%	5.75%		5.625%	5.625%		4.875%	4.875%	4.00%	4.00%
Percentage of face value price for issuance of senior notes							99.152%									99.178%
Interest payable dates										July 15 and January 15			April 1 and October 1			January 15 and July 15		April 1 and October 1			February 15 and August 15
Amortized deferred financing fees	4,278,000	3,923,000	8,516,000	7,527,000		2,400,000	5,400,000			14,000,000			8,500,000					7,700,000
Debt instrument, aggregate principal amount redeemed						131,300,000
Premium on redemption						10,800,000																10,100,000
Debt discount expensed						900,000
Debt instrument, principal balance	6,872,120,000		6,872,120,000		5,910,041,000			243,750,000	243,750,000		800,000,000	800,000,000		500,000,000	500,000,000				378,370,000	499,944,000
Debt instrument, carrying value	6,859,091,000		6,859,091,000		5,876,607,000			242,484,000	242,387,000		800,000,000	800,000,000		500,000,000	500,000,000				370,200,000	468,394,000
Call date								Aug. 15, 2014
Aggregate principal amount																			$ 121,500,000