Supplemental Disclosure of Cash Flow Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 62,721	$ 81,094
Income taxes paid, net of refunds	(128)	(107)
Net cash paid	66,592	48,928
Net cash paid	27,330	0
Prepaid expenses and other assets	(24,807)	(8,630)
Cash and cash equivalents	335,412		$ 222,647
Cash and escrow deposits – restricted	32,393		37,189
Long-term cash and escrow deposits – restricted	27,756		22,710
Total cash and cash equivalents and restricted cash and escrow deposits shown in the condensed consolidated statement of cash flows	395,561	120,791	$ 282,546	$ 277,322
Additions to property, plant and equipment and leasehold intangibles, net [Member]
Supplemental Cash Flow Information [Abstract]
Property, plant and equipment and leasehold intangibles, net	49,496	43,830
Accounts payable	(17,096)	(5,098)
Net cash paid	66,592	48,928
Acquisition of assets, net of related payables [Member]
Supplemental Cash Flow Information [Abstract]
Property, plant and equipment and leasehold intangibles, net	32,126	0
Other intangible assets, net	4,796	0
Net cash paid	27,330	0
Proceeds from sale of assets, net [Member]
Supplemental Cash Flow Information [Abstract]
Prepaid expenses and other assets	(579)	(356)
Assets held for sale	(18,758)	(5,621)
Property, plant and equipment and leasehold intangibles, net	(978)	0
Investments in unconsolidated ventures	20,084	26,301
Refundable entrance fees and deferred revenue	8,345	0
Other liabilities	425	0
(Gain) loss on sale of assets, net	(43,431)	603
Net cash received	(75,060)	(31,675)
Formation of Blackstone Joint Venture [Member]
Supplemental Cash Flow Information [Abstract]
Prepaid expenses and other assets	0	(8,173)
Investments in unconsolidated ventures	0	66,816
Capital and financing lease obligations	0	879,959
Deferred liabilities	0	7,504
Other liabilities	0	1,998
Property, plant and equipment and leasehold intangibles, net	0	(768,897)
Net cash paid	0	179,207
Assets designated as held for sale [Member]
Supplemental Cash Flow Information [Abstract]
Prepaid expenses and other assets	0	(106)
Assets held for sale	3,336	14,122
Property, plant and equipment and leasehold intangibles, net	3,336	14,016
Net	$ 0	$ 0