Borrowing Arrangements (Details 2) (USD $)	12 Months Ended				12 Months Ended				0 Months Ended	1 Months Ended				1 Months Ended					1 Months Ended					0 Months Ended	1 Months Ended				12 Months Ended		1 Months Ended				12 Months Ended			12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Feb. 01, 2013 Subsequent Event	Dec. 31, 2012 Senior Notes	Dec. 31, 2010 Senior Notes	Dec. 31, 2012 6.25% Senior Notes due 2013	Dec. 31, 2011 6.25% Senior Notes due 2013	Feb. 01, 2013 6.25% Senior Notes due 2013 Subsequent Event	Dec. 31, 2012 2.00% Senior Notes due 2018	Dec. 31, 2011 2.00% Senior Notes due 2018	Dec. 31, 2012 3.25% Senior Notes due 2022	Dec. 31, 2011 3.25% Senior Notes due 2022	Aug. 31, 2012 3.25% Senior Notes due 2022 3.25% Senior Notes due 2022, Issued August 2012	Dec. 31, 2012 3.25% Senior Notes due 2022 3.25% Senior Notes due 2022, Issued December 2012	Apr. 30, 2012 4.00% Senior Notes due 2019	Dec. 31, 2012 4.00% Senior Notes due 2019	Dec. 31, 2011 4.00% Senior Notes due 2019	Feb. 29, 2012 4.25% senior notes due 2022	Dec. 31, 2012 4.25% senior notes due 2022	Dec. 31, 2011 4.25% senior notes due 2022	Dec. 31, 2012 8.25% Senior Notes, Due 2012	Dec. 31, 2011 8.25% Senior Notes, Due 2012	Nov. 15, 2011 3 7/8% Convertible Senior Notes due 2011 upon maturity	Nov. 30, 2011 3 7/8% Convertible Senior Notes due 2011 upon maturity	May 31, 2011 4.750% Senior Notes due 2021	Dec. 31, 2012 4.750% Senior Notes due 2021	Dec. 31, 2011 4.750% Senior Notes due 2021	Dec. 31, 2012 6 1/2% Senior Notes due 2016	Dec. 31, 2011 6 1/2% Senior Notes due 2016	Nov. 30, 2011 3.125% Senior Notes due 2015	Dec. 31, 2012 3.125% Senior Notes due 2015	Dec. 31, 2011 3.125% Senior Notes due 2015	Nov. 30, 2010 3.125% Senior Notes due 2015	Dec. 31, 2012 6 3/4% Senior Notes due 2017	Dec. 31, 2010 6 3/4% Senior Notes due 2017	Dec. 31, 2011 6 3/4% Senior Notes due 2017	Dec. 31, 2010 6 5/8% Senior Notes due 2014	Dec. 31, 2010 7 1/8% Senior Notes due 2015	Dec. 31, 2012 NHP	Dec. 31, 2011 NHP 6.50% senior notes due 2011
Debt Instrument [Line Items]
Principal amount outstanding	$ 8,186,315,000	$ 6,180,443,000					$ 269,850,000	$ 269,850,000		$ 700,000,000	$ 0	$ 500,000,000	$ 0	$ 275,000,000	$ 225,000,000	$ 600,000,000	$ 600,000,000	$ 0	$ 600,000,000	$ 600,000,000	$ 0	$ 0	$ 72,950,000		$ 230,000,000	$ 700,000,000	$ 700,000,000	$ 700,000,000	$ 0	$ 200,000,000		$ 400,000,000	$ 400,000,000		$ 0		$ 225,000,000			$ 579,600,000
Aggregate shares of common stock issued for the conversion value in excess of the principal amount																								943,714	943,714
Debt assumed in connection with acquisition	412,825,000	3,651,089,000	125,320,000		3,500,000,000
Maturities of Senior Debt									270,000,000
Interest rate (as a percent)	9.00%		7.125%	6.25%			6.25%	6.25%		2.00%	2.00%	3.25%	3.25%	3.25%		400.00%	4.00%	4.00%	4.25%	4.25%	4.25%	8.25%	8.25%	3.875%	3.875%	4.75%	4.75%	4.75%	6.50%	6.50%		3.125%	3.125%	3.125%	6.75%	6.75%	6.75%	6.625%			6.50%
Redemption price as a percentage of par																													103.25%		99.528%				103.375%
Public offering price as percent of par										99.739%				99.027%	98.509%	9948.90%			99.214%							99.132%
Proceeds from issuance of debt										698,200,000				272,300,000	221,600,000	0			595,300,000							693,900,000					398,100,000
Extinguishment of debt, amount	155,400,000																																			1,400,000		71,700,000	142,700,000		339,000,000
Senior note redemption price as a percent of par																														103.25%								102.21%	103.56%
Loss on extinguishment of debt	(37,640,000)	(27,604,000)	(9,791,000)		39,700,000	8,900,000																								8,700,000
Principal amount of debt issued																															$ 400,000,000