Business Acquisitions (Details) - USD ($) $ in Millions	1 Months Ended	6 Months Ended
	Apr. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Business Acquisition [Line Items]
Purchase of redeemable noncontrolling interest		$ 131	$ 0
Acquisitions, net of cash acquired			(588)
Other acquisitions [Member]
Business Acquisition [Line Items]
Acquisitions, net of cash acquired		$ (107)	$ (588)
HomeServices [Member] | Real estate brokerage franchise business [Member]
Business Acquisition [Line Items]
Ownership Percentage Acquired	33.30%
Purchase of redeemable noncontrolling interest	$ 131