Debt (Details)	3 Months Ended	12 Months Ended
	Jun. 30, 2011 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) Community	Dec. 31, 2014 USD ($) Community	Dec. 31, 2013 USD ($)	Dec. 31, 2011 USD ($)
Debt Instrument [Line Items]
Debt		$ 6,122,413,000	$ 6,146,253,000
Long-term debt		5,886,809,000	5,877,854,000
Less current portion		235,604,000	$ 268,399,000
Weighted average interest rate			5.50%
Unamortized debt discount		$ (31,304,000)
Number of communities securing debt (in number of communities) | Community		28
Coupon interest		$ 173,484,000	$ 128,002,000	$ 96,131,000
Extinguishment of Debt, Amount			275,900,000
Long-term debt maturity [Abstract]
2016		418,233,000
2017		571,694,000
2018		1,462,653,000
2019		406,273,000
2020		698,199,000
Thereafter		4,991,168,000
Total obligations		8,548,220,000
Unamortized debt discount		(31,304,000)
Less amount representing interest		(2,394,503,000)
Total		6,122,413,000	6,146,253,000
Long-term debt, less current portion		3,459,371,000	3,340,971,000
Mortgages Payable [Member]
Debt Instrument [Line Items]
Debt		$ 3,246,513,000	$ 3,088,752,000
Maturity date, start		Mar. 28, 2016
Maturity date, end		Jan. 01, 2047
Weighted average interest rate		4.51%	4.84%
Unamortized debt premium		$ 3,300,000		$ 42,900,000
Long-term debt maturity [Abstract]
Total		3,246,513,000	$ 3,088,752,000
Capital Lease Obligations [Member]
Debt Instrument [Line Items]
Debt		$ 2,489,588,000	$ 2,649,226,000
Maturity date		Sep. 30, 2031
Weighted average interest rate		8.11%	8.57%
Unamortized debt discount		$ 0
Long-term debt maturity [Abstract]
2016		237,810,000
2017		263,671,000
2018		282,951,000
2019		262,800,000
2020		207,594,000
Thereafter		3,629,265,000
Total obligations		4,884,091,000
Unamortized debt discount		0
Less amount representing interest		(2,394,503,000)
Total		2,489,588,000	$ 2,649,226,000
Convertible Debt [Member]
Debt Instrument [Line Items]
Debt		$ 281,902,000	$ 269,300,000
Maturity date		Jun. 30, 2018
Weighted average interest rate			2.75%	2.75%	2.75%
Unamortized debt discount		$ 34,300,000	$ 46,900,000
Principal		316,300,000			$ 316,300,000
Proceeds from debt financing	$ 308,200,000
Initial conversion rate (in shares per $1,000 of principal)	34.1006
Equivalent initial conversion price (in dollars per share) | $ / shares	$ 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		11,732,000	10,902,000	10,131,000
Interest expense related to convertible notes		20,429,000	19,599,000	$ 18,828,000
Number of shares of common stock covered by hedging transactions (in shares) | shares	10,784,315
Number of warrants to acquire common stock sold to Hedge Counterparties (in shares) | shares	10,784,315
Strike price of warrants (in dollars per share) | $ / shares	$ 40.25
Net cost of hedging transaction	$ 31,900,000
Conversion rate per value of notes		$ 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%
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%
Long-term debt maturity [Abstract]
Unamortized debt discount		$ 34,300,000	46,900,000
Total		281,902,000	269,300,000
Construction Financing [Member]
Debt Instrument [Line Items]
Debt		$ 24,105,000	$ 50,118,000
Maturity date, start		Dec. 31, 2017
Maturity date, end		Dec. 31, 2019
Weighted average interest rate		4.84%	4.90%
Long-term debt maturity [Abstract]
Total		$ 24,105,000	$ 50,118,000
Notes Payable, Insurance Premiums [Member]
Debt Instrument [Line Items]
Debt		$ 0	$ 22,586,000
Maturity date		Oct. 31, 2015
Weighted average interest rate		2.82%	2.82%
Long-term debt maturity [Abstract]
Total		$ 0	$ 22,586,000
Other Notes Payable [Member]
Debt Instrument [Line Items]
Debt		$ 80,305,000	$ 66,271,000
Maturity date, start		Feb. 29, 2016
Maturity date, end		Feb. 01, 2020
Weighted average interest rate		5.16%	4.75%
Long-term debt maturity [Abstract]
Total		$ 80,305,000	$ 66,271,000
Long-term Debt [Member]
Debt Instrument [Line Items]
Debt		3,632,825,000
Unamortized debt discount		(31,304,000)
Long-term debt maturity [Abstract]
2016		180,423,000
2017		308,023,000
2018		1,179,702,000
2019		143,473,000
2020		490,605,000
Thereafter		1,361,903,000
Total obligations		3,664,129,000
Unamortized debt discount		(31,304,000)
Less amount representing interest		0
Total		3,632,825,000
First mortgage loan issued on April 9, 2014 [Member]
Debt Instrument [Line Items]
Maturity date			May 31, 2021
Weighted average interest rate			4.77%
Number of communities securing debt (in number of communities) | Community			20
Proceeds from debt financing			$ 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%
Number of communities securing debt (in number of communities) | Community			21
Proceeds from debt financing			$ 89,700,000
Debt extinguished with proceeds of public equity offering [Member]
Debt Instrument [Line Items]
Weighted average interest rate			5.50%
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Long-term debt maturity [Abstract]
Long-term debt, less current portion		$ 60,800,000