Revenue Recognition - Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended																12 Months Ended
		Dec. 31, 2020		Sep. 30, 2020		Jun. 30, 2020		Mar. 31, 2020		Dec. 31, 2019		Sep. 30, 2019		Jun. 30, 2019		Mar. 31, 2019		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Net revenues		$ 1,889		$ 1,909		$ 1,255		$ 1,168		$ 1,392		$ 1,629		$ 1,735		$ 1,114		$ 6,221	[1]	$ 5,870	[1]	$ 6,079	[1]
Realogy Franchise Group
Disaggregation of Revenue [Line Items]
Net revenues		298		314		227		220		269		319		331		239		1,059	[1]	1,158	[1]	1,198	[1]
Realogy Brokerage Group
Disaggregation of Revenue [Line Items]
Net revenues		1,461		1,479		933		869		1,040		1,222		1,331		816		4,742	[1]	4,409	[1]	4,607	[1]
Realogy Title Group
Disaggregation of Revenue [Line Items]
Net revenues		226		213		160		137		152		170		160		114		736	[1]	596	[1]	580	[1]
Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues		$ (96)	[2]	$ (97)	[2]	$ (65)	[2]	$ (58)	[2]	$ (69)	[3]	$ (82)	[3]	$ (87)	[3]	$ (55)	[3]	(316)	[1],[4]	(293)	[1],[4]	(306)	[1],[4]
Gross Commission Income
Disaggregation of Revenue [Line Items]
Net revenues	[5]																	4,669		4,330		4,533
Gross Commission Income | Realogy Franchise Group
Disaggregation of Revenue [Line Items]
Net revenues	[5]																	0		0		0
Gross Commission Income | Realogy Brokerage Group
Disaggregation of Revenue [Line Items]
Net revenues	[5]																	4,669		4,330		4,533
Gross Commission Income | Realogy Title Group
Disaggregation of Revenue [Line Items]
Net revenues	[5]																	0		0		0
Gross Commission Income | Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues	[5]																	0		0		0
Service revenue
Disaggregation of Revenue [Line Items]
Net revenues	[6]																	983		941		947
Service revenue | Realogy Franchise Group
Disaggregation of Revenue [Line Items]
Net revenues	[6]																	243		351		374
Service revenue | Realogy Brokerage Group
Disaggregation of Revenue [Line Items]
Net revenues	[6]																	26		11		9
Service revenue | Realogy Title Group
Disaggregation of Revenue [Line Items]
Net revenues	[6]																	714		579		564
Service revenue | Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues	[6]																	0		0		0
Franchise fees
Disaggregation of Revenue [Line Items]
Net revenues	[7]																	419		386		393
Franchise fees | Realogy Franchise Group
Disaggregation of Revenue [Line Items]
Net revenues	[7]																	725		668		688
Franchise fees | Realogy Brokerage Group
Disaggregation of Revenue [Line Items]
Net revenues	[7]																	0		0		0
Franchise fees | Realogy Title Group
Disaggregation of Revenue [Line Items]
Net revenues	[7]																	0		0		0
Franchise fees | Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues	[7]																	(306)		(282)		(295)
Other
Disaggregation of Revenue [Line Items]
Net revenues	[8]																	150		213		206
Other | Realogy Franchise Group
Disaggregation of Revenue [Line Items]
Net revenues	[8]																	91		139		136
Other | Realogy Brokerage Group
Disaggregation of Revenue [Line Items]
Net revenues	[8]																	47		68		65
Other | Realogy Title Group
Disaggregation of Revenue [Line Items]
Net revenues	[8]																	22		17		16
Other | Corporate and Other
Disaggregation of Revenue [Line Items]
Net revenues	[8]																	$ (10)		$ (11)		$ (11)

[1] Transactions between segments are eliminated in consolidation. Revenues for Realogy Franchise Group include intercompany royalties and marketing fees paid by Realogy Brokerage Group of $316 million, $293 million and $306 million for the years ended December 31, 2020, 2019 and 2018, respectively. Such amounts are eliminated through the Corporate and Other line.

[2] Represents the elimination of transactions primarily between Realogy Franchise Group and Realogy Brokerage Group.

[3] Represents the elimination of transactions primarily between Realogy Franchise Group and Realogy Brokerage Group.

[4] Includes the elimination of transactions between segments.

[5] Gross commission income at Realogy Brokerage Group is recognized at a point in time at the closing of a homesale transaction.

[6] Service revenue primarily consist of title and escrow fees at Realogy Title Group and are recognized at a point in time at the closing of a homesale transaction. Service revenue at Realogy Franchise Group includes relocation fees, which are recognized as revenue when or as the related performance obligation is satisfied dependent on the type of service performed, and fees related to leads and related services, which are recognized at a point in time at the closing of a homesale transaction or at the completion of the related service.

[7] Franchise fees at Realogy Franchise Group 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).

[8] Other revenue includes brand marketing funds received at Realogy Franchise Group from franchisees, third-party listing fees in 2019 and 2018, and other miscellaneous revenues across all of the business segments.