Variable Interest Entities and Investment in Unconsolidated Ventures - Equity Method Investments (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Operations Information
Resident fee revenue	$ 793	$ 1,354	$ 1,133
Facility operating expense	(592)	(946)	(779)
Net income (loss)	(39)	(81)	$ (4)
Balance Sheet Information
Current assets	66	164
Noncurrent assets	1,148	4,050
Current liabilities	563	672
Noncurrent liabilities	$ 715	$ 2,813