Debt (Senior Notes) (Narrative) (Details) (USD $)	12 Months Ended			0 Months Ended				0 Months Ended		12 Months Ended		0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended		0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 29, 2012 8.0% Senior Notes [Member]	Apr. 13, 2012 8.0% Senior Notes [Member]	Jul. 24, 2009 8.0% Senior Notes [Member]	Dec. 31, 2013 8.0% Senior Notes [Member]	Apr. 13, 2012 8.25% Senior Notes [Member]	Jul. 24, 2009 8.25% Senior Notes [Member]	Dec. 31, 2013 8.25% Senior Notes [Member]	Dec. 31, 2012 8.25% Senior Notes [Member]	Jul. 13, 2012 5.75% Senior Notes [Member]	Dec. 31, 2013 5.75% Senior Notes [Member]	Dec. 31, 2012 5.75% Senior Notes [Member]	Sep. 28, 2012 5.625% Senior Notes [Member]	Dec. 31, 2013 5.625% Senior Notes [Member]	Dec. 31, 2012 5.625% Senior Notes [Member]	Apr. 13, 2012 Senior Notes [Member]	Jul. 24, 2009 Senior Notes [Member]
Debt Instrument [Line Items]
Unsecured senior notes						$ 375,000,000			$ 375,000,000			$ 800,000,000			$ 500,000,000				$ 750,000,000
Debt instrument, maturity date						Aug. 15, 2016			Aug. 15, 2019	Aug. 15, 2019		Jul. 15, 2020	Jul. 15, 2020		Oct. 01, 2019	Oct. 01, 2019
Debt instrument, interest rate, stated percentage						8.00%	8.00%		8.25%	8.25%		5.75%	5.75%		5.625%	5.625%
Percentage of face value price for issuance of senior notes						99.33%			99.152%
Interest payable dates												July 15 and January 15			October 1 and April 1				February 15 and August 15
Amortized deferred financing fees	15,560,000	12,870,000	9,188,000	3,400,000					5,400,000			14,000,000			8,500,000			4,300,000
Net proceeds of offering after deducting discounts																			727,800,000
Debt instrument, aggregate principal amount redeemed				243,800,000	131,300,000			131,300,000
Premium on redemption				14,600,000														21,300,000
Debt discount expensed				1,000,000														1,500,000
Debt instrument, Principal Balance	5,910,041,000	5,440,073,000								243,750,000	243,750,000		800,000,000	800,000,000		500,000,000	500,000,000
Debt, Carrying Value	$ 5,876,607,000	$ 5,356,103,000								$ 242,387,000	$ 242,205,000		$ 800,000,000	$ 800,000,000		$ 500,000,000	$ 500,000,000