Assets Held for Sale, Net and Discontinued Operations - Summary of Loss from Discontinued Operations (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($) Property	Dec. 31, 2014 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income (loss) from discontinued operations	$ 9,691,000	$ 204,671,000	$ (31,706,000)
Amortization of loss and loss on termination of cash flow hedges	0	0	3,000,000
Discontinued Operations, Held-for-sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues	3,838,000	65,796,000	178,887,000
Expenses	(3,189,000)	(49,251,000)	(115,773,000)
Depreciation and amortization	0	0	(36,709,000)
Impairment provision	0	(7,749,000)	(37,867,000)
Operating income (loss)	649,000	8,796,000	(11,462,000)
Net gain from sale of real estate	9,687,000	200,243,000	4,144,000
Loss on extinguishment of debt	(308,000)	(2,042,000)	(4,818,000)
Gain on insurance and retirements	(412,000)	2,816,000	4,791,000
Other income (expense)	75,000	(5,142,000)	(24,361,000)
Income (loss) from discontinued operations	$ 9,691,000	$ 204,671,000	$ (31,706,000)
Senior Housing Property | Discontinued Operations, Disposed of by Sale
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties sold | Property		38