Property, Plant and Equipment and Leasehold Intangibles, Net (Details) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) Community	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) Community	Dec. 31, 2014 USD ($) Community	Dec. 31, 2013 USD ($)
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	$ 10,574,411				$ 10,295,498				$ 10,574,411	$ 10,295,498
Accumulated depreciation and amortization	(2,543,035)				(1,905,993)				(2,543,035)	(1,905,993)
Property, plant and equipment and leasehold intangibles, net	8,031,376				8,389,505				8,031,376	8,389,505
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment, non-cash charge	57,941	$ 0	$ 0	$ 0	9,992	$ 0	$ 0	$ 0	57,941	9,992	$ 12,891
Depreciation and amortization expense on property, plant and equipment and leasehold intangibles									721,000	$ 529,100	$ 264,100
Resident And Leasehold Operating Intangibles Future Amortization Expense [Abstract]
2016	19,390								19,390
2017	13,011								13,011
2018	7,603								7,603
2019	6,247								6,247
2020	4,345								4,345
Thereafter	12,663								12,663
Total	63,259								63,259
Number of communities purchased or sold | Community										4
Aggregate selling price									82,900	$ 9,200
Goodwill	$ 725,696				736,805				$ 725,696	736,805
Communities classified as held for sale | Community	17								17
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	$ 486,567				475,485				$ 486,567	475,485
Buildings and Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	5,260,826				5,017,991				5,260,826	5,017,991
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	100,430				56,515				100,430	56,515
Furniture and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	895,447				735,837				895,447	735,837
Resident and Leasehold Operating Intangibles [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	783,434				852,746				783,434	852,746
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	138,054				99,408				138,054	99,408
Assets Under Capital and Financing Leases [Member]
Property, Plant and Equipment [Line Items]
Property, plant and equipment and leasehold intangibles gross	2,909,653				$ 3,057,516				2,909,653	$ 3,057,516
Property, Plant and Equipment [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment, non-cash charge									24,300
Communities sold during 2015 [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment, non-cash charge									$ 18,400
Resident And Leasehold Operating Intangibles Future Amortization Expense [Abstract]
Number of communities purchased or sold | Community									17
Goodwill	8,100								$ 8,100
Disposal Group, Held-for-sale, Not Discontinued Operations [Member]
Impaired Long-Lived Assets Held and Used [Line Items]
Asset impairment, non-cash charge									15,000
Resident And Leasehold Operating Intangibles Future Amortization Expense [Abstract]
Goodwill	$ 12,200								$ 12,200
Communities classified as held for sale | Community	17								17
Resident lease intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life										1 year
Below Market Operating Lease Intangibles [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life										9 years