Supplemental Disclosure of Cash Flow Information - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Elements [Abstract]
Interest paid	$ 294,758	$ 349,535	$ 360,960
Income taxes paid, net of refunds	1,038	2,047	2,952
Net cash paid	213,887	333,647	411,051
Net cash paid	5,196	12,157	191,216
Prepaid expenses and other assets	21,970	2,954	51,079
Loss on facility lease termination	14,276	0	0
Additions to property, plant and equipment and leasehold intangibles, net
Supplemental Cash Flow Elements [Abstract]
Property, plant and equipment and leasehold intangibles, net	221,476	300,113	448,682
Accounts payable	(7,589)	33,534	(37,631)
Net cash paid	213,887	333,647	411,051
Acquisition of assets, net of related payables
Supplemental Cash Flow Elements [Abstract]
Property, plant and equipment and leasehold intangibles, net	0	19,457	198,558
Prepaid expenses and other assets	0	0	(53,405)
Other intangible assets, net	5,196	(7,300)	(7,294)
Long-term debt	0	0	(101,558)
Capital and financing lease obligations	0	0	155,230
Other liabilities	0	0	(315)
Net cash paid	5,196	12,157	191,216
Proceeds from sale of assets, net
Supplemental Cash Flow Elements [Abstract]
Long-term debt	8,547	0	0
Prepaid expenses and other assets	(17,072)	(4,543)	25,780
Assets held for sale	(20,952)	(289,452)	0
Property, plant and equipment and leasehold intangibles, net	(155,723)	0	(82,953)
Investments in unconsolidated ventures	52,548	0	0
Other liabilities	(1,058)	3,281	(960)
Capital and financing lease obligations	157,963	0	8,907
Refundable entrance fees and deferred revenue	30,771	0	0
Gain on sale of assets, net	(19,273)	(7,218)	0
Loss on facility lease termination	(1,162)	0	0
Net cash received	(70,507)	(297,932)	(49,226)
Formation of the Blackstone Venture
Supplemental Cash Flow Elements [Abstract]
Other liabilities	(1,998)	0	0
Prepaid expenses and other assets	(8,173)	0	0
Property, plant and equipment and leasehold intangibles, net	(768,897)	0	0
Investments in unconsolidated ventures	66,816	0	0
Capital and financing lease obligations	879,959	0	0
Deferred liabilities	7,504	0	0
Net cash paid	$ 179,207	$ 0	$ 0