Debt (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2011	Dec. 31, 2014	Dec. 31, 2011
Debt Instrument [Line Items]
Debt	$ 6,165,956,000	$ 2,606,578,000			$ 6,165,956,000
Long-term debt	5,893,691,000	2,404,624,000			5,893,691,000
Less current portion	272,265,000	201,954,000			272,265,000
Weighted average interest rate	5.50%				5.50%
Unamortized debt discount	15,718,000				15,718,000
Coupon interest	128,002,000	96,131,000	98,183,000
Extinguishment of Debt, Amount	275,900,000
Long-term debt maturity [Abstract]
2015	398,756,000				398,756,000
2016	384,961,000				384,961,000
2017	834,113,000				834,113,000
2018	1,585,148,000				1,585,148,000
2019	441,335,000				441,335,000
Thereafter	4,912,439,000				4,912,439,000
Total obligations	8,556,752,000				8,556,752,000
Unamortized debt discount	15,718,000				15,718,000
Less amount representing interest	(2,406,514,000)				(2,406,514,000)
Total	6,165,956,000	2,606,578,000			6,165,956,000
Mortgages Payable [Member]
Debt Instrument [Line Items]
Debt	3,105,410,000	2,037,649,000			3,105,410,000
Maturity date, start	Mar. 31, 2015
Maturity date, end	Jan. 01, 2047
Weighted average interest rate	4.84%	4.12%			4.84%
Unamortized debt premium	59,600,000	1,300,000			59,600,000
Long-term debt maturity [Abstract]
Total	3,105,410,000	2,037,649,000			3,105,410,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt	2,649,226,000	299,824,000			2,649,226,000
Maturity date	Sep. 30, 2030
Weighted average interest rate	8.57%	8.14%			8.57%
Unamortized debt discount	0				0
Long-term debt maturity [Abstract]
2015	246,992,000				246,992,000
2016	323,446,000				323,446,000
2017	280,077,000				280,077,000
2018	283,757,000				283,757,000
2019	291,493,000				291,493,000
Thereafter	3,629,975,000				3,629,975,000
Total obligations	5,055,740,000				5,055,740,000
Unamortized debt discount	0				0
Less amount representing interest	(2,406,514,000)				(2,406,514,000)
Total	2,649,226,000	299,824,000			2,649,226,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Debt	272,345,000	261,443,000			272,345,000
Maturity date	Jun. 30, 2018
Weighted average interest rate	2.75%	2.75%			2.75%	2.75%
Unamortized debt discount	43,900,000	54,800,000			43,900,000
Principal	316,300,000				316,300,000	316,300,000
Net proceeds from issuance				308,200,000
Initial conversion rate (in shares per $1,000 of principal)				34.1006
Equivalent initial conversion price (in dollars per share)				$ 29.325
Conversion terms				The Notes are convertible at an initial conversion rate of 34.1006 shares of Company common stock per $1,000 principal amount of Notes (equivalent to an initial conversion price of approximately $29.325 per share), subject to adjustment. Holders may convert their Notes at their option prior to the close of business on the second trading day immediately preceding the stated maturity date only under the following circumstances: (i) during any fiscal quarter commencing after the fiscal quarter ending September 30, 2011, if the last reported sale price of the Company's common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the preceding fiscal quarter is greater than or equal to 130% of the applicable conversion price on each applicable trading day; (ii) during the five business day period after any five consecutive trading day period (the "measurement period"), in which the trading price per $1,000 principal amount of notes for each trading day of that measurement period was less than 98% of the product of the last reported sale price of the Company's common stock and the applicable conversion rate on each such day; or (iii) upon the occurrence of specified corporate events. On and after March 15, 2018, until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their Notes at any time, regardless of the foregoing circumstances. Unconverted Notes mature at par in June 2018.
Imputed interest rate				7.50%
Expected life of convertible debt				7 years
Coupon interest	8,697,000	8,697,000	8,697,000
Amortization of discount	10,902,000	10,131,000	9,415,000
Interest expense related to convertible notes	19,599,000	18,828,000	18,112,000
Number of shares of common stock covered by hedging transactions (in shares)				10,784,315
Number of warrants to acquire common stock sold to Hedge Counterparties (in shares)				10,784,315
Strike price of warrants (in dollars per share)				$ 40.25
Net cost of hedging transaction				31,900,000
Conversion rate per value of notes	1,000				1,000
Number of trading days for pricing	20 days
Number of consecutive trading days	30 days
Percentage minimum of applicable conversion price (in hundredths)	130.00%				130.00%
Number of consecutive trading days less than 98% of test period	5 days
Applicable percentage rate for five day consecutive trading days (in hundredths)	98.00%				98.00%
Long-term debt maturity [Abstract]
Unamortized debt discount	43,900,000	54,800,000			43,900,000
Total	272,345,000	261,443,000			272,345,000
Construction Financing [Member]
Debt Instrument [Line Items]
Debt	50,118,000	4,476,000			50,118,000
Maturity date, start	Dec. 31, 2017
Maturity date, end	Dec. 31, 2019
Weighted average interest rate	4.90%	6.22%			4.90%
Long-term debt maturity [Abstract]
Total	50,118,000	4,476,000			50,118,000
Notes Payable, Insurance Premiums [Member]
Debt Instrument [Line Items]
Debt	22,586,000	3,186,000			22,586,000
Maturity date	Oct. 31, 2015
Weighted average interest rate	2.82%	2.65%			2.82%
Long-term debt maturity [Abstract]
Total	22,586,000	3,186,000			22,586,000
Other Notes Payable [Member]
Debt Instrument [Line Items]
Debt	66,271,000	0			66,271,000
Maturity date, start	Aug. 29, 2015
Maturity date, end	Apr. 15, 2016
Weighted average interest rate	4.75%				4.75%
Long-term debt maturity [Abstract]
Total	66,271,000	0			66,271,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt	3,516,730,000				3,516,730,000
Unamortized debt discount	15,718,000				15,718,000
Long-term debt maturity [Abstract]
2015	151,764,000				151,764,000
2016	61,515,000				61,515,000
2017	554,036,000				554,036,000
2018	1,301,391,000				1,301,391,000
2019	149,842,000				149,842,000
Thereafter	1,282,464,000				1,282,464,000
Total obligations	3,501,012,000				3,501,012,000
Unamortized debt discount	15,718,000				15,718,000
Less amount representing interest	0				0
Total	3,516,730,000				3,516,730,000
First Mortgage Loan Issued on April 3, 2013 [Member]
Debt Instrument [Line Items]
Maturity date		Apr. 30, 2018
Number of communities securing debt (in number of communities)		1
Description of variable rate basis		variable rate equal to 30-day LIBOR plus a margin of 275 basis points
Basis spread on variable rate basis		0.275%
Principal		25,000,000
Extinguishment of Debt, Amount		29,000,000
First Mortgage Loan Issued on April 12, 2013 [Member]
Debt Instrument [Line Items]
Maturity date		May 31, 2023
Number of communities securing debt (in number of communities)		23
Description of variable rate basis		variable rate equal to 30-day LIBOR plus a margin of 246 basis points
Basis spread on variable rate basis		0.246%
Principal		259,000,000
Extinguishment of Debt, Amount		275,200,000
Derivative, Remaining Maturity		5 years
Derivative, Cap Interest Rate		5.03%
Amortization period (in years)		30 years
First Mortgage Loan Issued on April 22, 2013 [Member]
Debt Instrument [Line Items]
Maturity date		Apr. 30, 2018
Number of communities securing debt (in number of communities)		2
Description of variable rate basis		variable rate equal to 30-day LIBOR plus a margin of 275 basis points
Basis spread on variable rate basis		0.275%
Principal		28,000,000
Extinguishment of Debt, Amount		35,100,000
First Mortgage Loan Issued on May 30, 2013 [Member]
Debt Instrument [Line Items]
Number of communities securing debt (in number of communities)		8
Description of variable rate basis		variable rate equal to 30-day LIBOR plus a margin of 289 basis points
Basis spread on variable rate basis		0.289%
Principal		84,100,000
Extinguishment of Debt, Amount		100,900,000
Derivative, Remaining Maturity		5 years
Derivative, Cap Interest Rate		4.68%
Term of loan		10 years
First Mortgage Loan Issued on August 1, 2013 [Member]
Debt Instrument [Line Items]
Number of communities securing debt (in number of communities)		4
Description of variable rate basis		variable rate equal to 30-day LIBOR plus a margin ranging from 226 to 288 basis points
Principal		172,100,000
Extinguishment of Debt, Amount		142,000,000
Amortization period (in years)		30 years
First Mortgage Loan Issued on August 1, 2013 [Member] | Minimum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate basis		0.226%
First Mortgage Loan Issued on August 1, 2013 [Member] | Maximum [Member]
Debt Instrument [Line Items]
Basis spread on variable rate basis		0.288%
Loans Maturing in August 2020 [Member]
Debt Instrument [Line Items]
Maturity date		Aug. 31, 2020
Principal		75,000,000
Loans Maturing in August 2023 [Member]
Debt Instrument [Line Items]
Maturity date		Aug. 31, 2023
Principal		97,100,000
First Mortgage Loan Financing Acquisition [Member]
Debt Instrument [Line Items]
Principal		60,800,000
First Mortgage Loan Assumed in Acquisition [Member]
Debt Instrument [Line Items]
Maturity date		May 31, 2017
Weighted average interest rate		5.75%
Principal		52,700,000
First Mortgage Loan Issued On October 1 2013 [Member]
Debt Instrument [Line Items]
Weighted average interest rate		5.32%
Number of communities securing debt (in number of communities)		1
Principal		8,100,000
Term of loan		7 years
First Mortgage Loan Issued On December 18 2013 [Member]
Debt Instrument [Line Items]
Maturity date		Dec. 31, 2018
Weighted average interest rate		4.50%
Number of communities securing debt (in number of communities)		2
Principal		14,000,000
Extinguishment of Debt, Amount		14,200,000
First Mortgage Loan Issued On December 20 2013 [Member]
Debt Instrument [Line Items]
Maturity date		Jan. 31, 2019
Weighted average interest rate		4.35%
Number of communities securing debt (in number of communities)		2
Principal		25,000,000
Extinguishment of Debt, Amount		30,300,000
First mortgage loan issued on April 9, 2014 [Member]
Debt Instrument [Line Items]
Maturity date, end	May 31, 2021
Weighted average interest rate	4.77%				4.77%
Number of communities securing debt (in number of communities)	20
Principal	146,000,000				146,000,000
Extinguishment of Debt, Amount	140,000,000
First mortgage loan issued in October, 2014 [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.60%				4.60%
Number of communities securing debt (in number of communities)	21
Principal	89,700,000				89,700,000
Debt extinguished with proceeds of public equity offering [Member]
Debt Instrument [Line Items]
Weighted average interest rate	5.50%				5.50%
Extinguishment of Debt, Amount					275,900,000
RIDEA JV [Member]
Debt Instrument [Line Items]
Extinguishment of Debt, Amount	$ 68,000,000