Summary of Significant Accounting Policies (Details) (USD $) In Thousands	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2011		Jun. 30, 2010		Jun. 30, 2011		Jun. 30, 2010		Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Reimbursed costs incurred on behalf of managed communities	$ 17,871		$ 16,546		$ 35,351		$ 33,126		$ 67,271	$ 77,206	$ 73,250
Total revenue	583,299	[1]	565,518	[1]	1,170,219	[1]	1,126,522	[1]	2,280,535	2,100,274	2,001,304
Costs incurred on behalf of managed communities	17,871		16,546		35,351		33,126		67,271	77,206	73,250
Total operating expense	554,436		541,774		1,129,356		1,086,940		2,214,541	2,070,494	2,241,447
Deferred revenue	52,100				52,100				52,900
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Insurance deductibles, per claim	150				150
Amount of claims below which the company is self-insured	150				150
Amortized cost basis of marketable securities - restricted	31,800				31,800
Scenario, Previously Reported [Member]
Reimbursed costs incurred on behalf of managed communities			0				0		0	0	0
Total revenue			548,972				1,093,396		2,213,264	2,023,068	1,928,054
Costs incurred on behalf of managed communities			0				0		0	0	0
Total operating expense			525,228				1,053,814		2,147,270	1,993,288	2,168,197
Restatement Adjustment [Member]
Reimbursed costs incurred on behalf of managed communities			16,546				33,126		67,271	77,206	73,250
Total revenue			16,546				33,126		67,271	77,206	73,250
Costs incurred on behalf of managed communities			16,546				33,126		67,271	77,206	73,250
Total operating expense			16,546				33,126		67,271	77,206	73,250
Carrying (Reported) Amount, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	2,400,000				2,400,000				2,600,000
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 2,400,000				$ 2,400,000				$ 2,500,000

[1] All revenue is earned from external third parties in the United States.