Debt (Details) (USD $)	12 Months Ended					12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		3 Months Ended	12 Months Ended					12 Months Ended			12 Months Ended		12 Months Ended		12 Months Ended		12 Months Ended		0 Months Ended	12 Months Ended			12 Months Ended							12 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Mortgages Payable [Member]	Dec. 31, 2012 Mortgages Payable [Member]	Dec. 31, 2012 $150 Million Series A Notes Payable [Member] Community	Dec. 31, 2013 $150 Million Series A Notes Payable [Member]	Dec. 31, 2012 Discount Mortgage Note payable due June 2013 [Member]	Dec. 31, 2013 Discount Mortgage Note payable due June 2013 [Member]	Dec. 31, 2012 Variable Rate Tax Exempt Bonds [Member]	Dec. 31, 2013 Variable Rate Tax Exempt Bonds [Member]	Dec. 31, 2013 Capital Lease Obligations [Member]	Dec. 31, 2012 Capital Lease Obligations [Member]	Jun. 30, 2011 Convertible Debt [Member] Dollarsperunit	Dec. 31, 2013 Convertible Debt [Member]	Dec. 31, 2012 Convertible Debt [Member]	Dec. 31, 2011 Convertible Debt [Member]	Dec. 31, 2013 Construction Financing [Member]	Dec. 31, 2012 Construction Financing [Member]	Dec. 31, 2013 Notes Payable, Insurance Premiums [Member]	Dec. 31, 2012 Notes Payable, Insurance Premiums [Member]	Dec. 31, 2013 Long-term Debt [Member]	Dec. 31, 2012 First Mortgage Loan Issued in January 2012 [Member]	Jan. 05, 2012 First Mortgage Loan Issued in January 2012 [Member]	Dec. 31, 2012 First Mortgage Loan Issued in February 2012 [Member]	Feb. 29, 2012 First Mortgage Loan Issued in February 2012 [Member]	Dec. 31, 2012 Mortgage Loan Issued to Finance Acquisition [Member]	Feb. 02, 2012 Mortgage Loan Issued to Finance Acquisition [Member]	Dec. 31, 2012 First Mortgage Loan Issued in June 2012 [Member] Community	Jun. 29, 2012 First Mortgage Loan Issued in June 2012 [Member]	Dec. 28, 2012 First Mortgage Loan Issued in December 2012 [Member]	Dec. 31, 2012 First Mortgage Loan Issued in December 2012 [Member] Community	Dec. 31, 2012 Seller - Financed Debt [Member]	Feb. 02, 2012 Seller - Financed Debt [Member]	Dec. 31, 2013 First Mortgage Loan Issued on April 3, 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued on April 12, 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued on April 22, 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued on May 30, 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued on August 1, 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued on August 1, 2013 [Member] Minimum [Member]	Dec. 31, 2013 First Mortgage Loan Issued on August 1, 2013 [Member] Maximum [Member]	Dec. 31, 2013 Loans Maturing in August 2020 [Member]	Dec. 31, 2013 Loans Maturing in August 2023 [Member]	Dec. 31, 2013 First Mortgage Loan Financing Acquisition [Member]	Dec. 31, 2013 First Mortgage Loan Assumed in Acquisition [Member]	Dec. 31, 2013 First Mortgage Loan Issued On October 1 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued On December 18 2013 [Member] Community	Dec. 31, 2013 First Mortgage Loan Issued On December 20 2013 [Member] Community
Debt Instrument [Line Items]
Debt	$ 2,606,578,000	$ 2,599,369,000		$ 2,037,649,000	$ 1,701,515,000	$ 144,384,000	$ 0	$ 80,533,000	$ 0	$ 99,847,000	$ 0	$ 299,824,000	$ 319,745,000		$ 261,443,000	$ 251,312,000		$ 4,476,000	$ 1,280,000	$ 3,186,000	$ 753,000	$ 2,306,754,000
Less current portion	201,954,000	509,543,000
Long-term debt	2,404,624,000	2,089,826,000
Maturity date						Aug. 31, 2013		Jun. 30, 2013		Dec. 31, 2032		Dec. 31, 2026			Jun. 30, 2018					Dec. 31, 2014			Jan. 31, 2017		Feb. 28, 2017				Jun. 30, 2017						Apr. 30, 2018	May 31, 2023	Apr. 30, 2018					Aug. 31, 2020	Aug. 31, 2023		May 31, 2017		Dec. 31, 2018	Jan. 31, 2019
Maturity date, start				Dec. 31, 2014														Dec. 31, 2017
Maturity date, end				Dec. 31, 2023														Dec. 31, 2027
Weighted average interest rate				4.12%	4.62%			2.56%		1.65%		8.14%	8.16%		2.75%	2.75%	2.75%	6.22%	8.00%	2.65%	2.81%																								5.75%	5.32%	4.50%	4.35%
Unamortized debt premium				1,300,000
Unamortized debt discount	(53,528,000)				300,000			1,000,000				0			54,800,000	65,000,000						(53,528,000)
Number of communities securing debt (in number of communities)						5																							2			9			1	23	2	8	4							1	2	2
Amount of cash collateral securing debt						3,000,000
Description of variable rate basis						LIBOR plus 0.88%																	variable rate equal to 30-day LIBOR plus a margin of 300 basis points		variable rate equal to 30-day LIBOR plus a margin of 275 basis points				bears interest at a variable rate equal to 30-day LIBOR plus a margin of 425 basis points			variable rate equal to 30-day LIBOR plus a margin of 259 basis points			variable rate equal to 30-day LIBOR plus a margin of 275 basis points	variable rate equal to 30-day LIBOR plus a margin of 246 basis points	variable rate equal to 30-day LIBOR plus a margin of 275 basis points	variable rate equal to 30-day LIBOR plus a margin of 289 basis points	variable rate equal to 30-day LIBOR plus a margin ranging from 226 to 288 basis points
Basis spread on variable rate basis						0.88%																		3.00%		2.75%				4.25%	2.59%				0.275%	0.246%	0.275%	0.289%		0.226%	0.288%
Principal						150,000,000									316,300,000		316,300,000							63,000,000		20,000,000		77,900,000		15,000,000	171,300,000			15,000,000	25,000,000	259,000,000	28,000,000	84,100,000	172,100,000			75,000,000	97,100,000	60,800,000	52,700,000	8,100,000	14,000,000	25,000,000
Current Portion of Mortgage Loans with Extension Options	140,000,000
Maximum term of debt extension	1 year
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	121,325,000	128,338,000	124,873,000												8,697,000	8,697,000	4,759,000
Amortization of discount															10,131,000	9,415,000	4,456,000
Interest expense related to convertible notes															18,828,000	18,112,000	9,215,000
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
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%
Extinguishment of Debt, Amount																							62,800,000						15,000,000			37,400,000			29,000,000	275,200,000	35,100,000	100,900,000	142,000,000								14,200,000	30,300,000
Interest rate terms																											75% of it bears interest at a fixed rate of 4.2% and the remaining 25% bears interest at a variable rate of 30-day LIBOR plus a margin of 276 basis points						bore interest at a fixed rate of 7.0%
Derivative, Remaining Maturity																																				5 years		5 years
Derivative, Cap Interest Rate																																				5.03%		4.68%
Term of loan																											10 years				10 years		2 years					10 years								7 years
Number of recently acquired communities securing mortgage notes																																8
Amortization period (in years)																																				30 years			30 years
Long-term debt maturity [Abstract]
2014	235,272,000											56,157,000										179,115,000
2015	92,540,000											54,853,000										37,687,000
2016	118,435,000											47,710,000										70,725,000
2017	447,782,000											75,620,000										372,162,000
2018	818,592,000											35,545,000										783,047,000
Thereafter	1,100,118,000											182,572,000										917,546,000
Total obligations	2,812,739,000											452,457,000										2,360,282,000
Unamortized debt discount	(53,528,000)				300,000			1,000,000				0			54,800,000	65,000,000						(53,528,000)
Less amount representing interest	(152,633,000)											(152,633,000)										0
Total	$ 2,606,578,000	$ 2,599,369,000		$ 2,037,649,000	$ 1,701,515,000	$ 144,384,000	$ 0	$ 80,533,000	$ 0	$ 99,847,000	$ 0	$ 299,824,000	$ 319,745,000		$ 261,443,000	$ 251,312,000		$ 4,476,000	$ 1,280,000	$ 3,186,000	$ 753,000	$ 2,306,754,000