Basis Of Presentation Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2]	$ (1,629)	$ (1,676)	$ (4,478)	$ (4,725)
Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	(1,201)	(1,246)	(3,310)	(3,536)
Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	(269)	(268)	(710)	(728)
Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	(108)	(109)	(290)	(302)
Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	(51)	(53)	(168)	(159)
Real Estate Franchise Services
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2]	(216)	(221)	(613)	(634)
Real Estate Franchise Services | Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	0	0	0	0
Real Estate Franchise Services | Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	0	0	0	0
Real Estate Franchise Services | Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	(186)	(189)	(505)	(531)
Real Estate Franchise Services | Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	(30)	(32)	(108)	(103)
Company Owned Brokerage Services
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2]	(1,222)	(1,268)	(3,369)	(3,593)
Company Owned Brokerage Services | Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	(1,201)	(1,246)	(3,310)	(3,536)
Company Owned Brokerage Services | Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	(2)	(3)	(7)	(7)
Company Owned Brokerage Services | Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	0	0	0	0
Company Owned Brokerage Services | Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	(19)	(19)	(52)	(50)
Relocation Services
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2]	(103)	(108)	(276)	(292)
Relocation Services | Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	0	0	0	0
Relocation Services | Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	(102)	(107)	(273)	(289)
Relocation Services | Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	0	0	0	0
Relocation Services | Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	(1)	(1)	(3)	(3)
Title and Settlement Services
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2]	(170)	(162)	(444)	(444)
Title and Settlement Services | Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	0	0	0	0
Title and Settlement Services | Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	(165)	(158)	(430)	(432)
Title and Settlement Services | Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	0	0	0	0
Title and Settlement Services | Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	(5)	(4)	(14)	(12)
Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues	[1],[2],[7]	(82)	(83)	(224)	(238)
Corporate and Other | Gross commission income
Disaggregation of Revenue [Line Items]
Net revenues	[3]	0	0	0	0
Corporate and Other | Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[4]	0	0	0	0
Corporate and Other | Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[5]	78	80	215	229
Corporate and Other | Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]	$ (4)	$ 3	$ (9)	$ 9
Minimum | Company Owned Brokerage Services
Disaggregation of Revenue [Line Items]
New Development Period				18 months
Maximum | Company Owned Brokerage Services
Disaggregation of Revenue [Line Items]
New Development Period				24 months

[1] Revenues for the Relocation Services segment include intercompany referral commissions paid by the Company Owned Real Estate Brokerage Services segment of $11 million and $29 million for the three and nine months ended September 30, 2019, respectively, and $10 million and $30 million for the three and nine months ended September 30, 2018, respectively. Such amounts are recorded as contra-revenues by the Company Owned Real Estate Brokerage Services segment. There are no other material intersegment transactions.

[2] Transactions between segments are eliminated in consolidation. Revenues for the Real Estate Franchise Services segment include intercompany royalties and marketing fees paid by the Company Owned Real Estate Brokerage Services segment of $82 million and $224 million for the three and nine months ended September 30, 2019, respectively, and $83 million and $238 million for the three and nine months ended September 30, 2018, respectively. Such amounts are eliminated through the Corporate and Other line.

[3] Consists primarily of revenues related to gross commission income at the Company Owned Real Estate Brokerage Services segment which is recognized at a point in time at the closing of a homesale transaction.

[4] Service revenue primarily consists of title and escrow fees at the Title and Settlement Services segment, which are recognized at a point in time at the closing of a homesale transaction, and relocation fees at the Relocation Services segment, which are recognized as revenue when or as the related performance obligation is satisfied, which is dependent on the type of service performed.

[5] Franchise fees at the Real Estate Franchise Services segment primarily include domestic royalties which are recognized at a point in time when the underlying franchisee revenue is earned (upon close of the homesale transaction).

[6] Other revenue is comprised of brand marketing funds received at the Real Estate Franchise Services segment from franchisees, third-party listing fees and other miscellaneous revenues across all of the business segments.

[7] Includes the elimination of transactions between segments.