Franchising and Marketing Activities (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($) franchisedandcompanyownedoffices	Dec. 31, 2022 USD ($) franchisedandcompanyownedoffices	Dec. 31, 2021 USD ($) franchisedandcompanyownedoffices	Dec. 31, 2023 Brokerage_Offices	Dec. 31, 2020 franchisedandcompanyownedoffices
Franchisor Disclosure [Line Items]
Initial franchise and area development fees | $	$ 5	$ 4	$ 5
Annual volume incentives from Real Estate Franchisees | $	43	61	87
Brand Marketing Fund Revenue | $	$ 82	$ 89	$ 92
Franchise Group
Franchisor Disclosure [Line Items]
Number of offices	18,303	19,824	20,355		19,386
Franchise Group | Century 21®
Franchisor Disclosure [Line Items]
Number of offices	11,972	13,611	14,246
Franchise Group | ERA®
Franchisor Disclosure [Line Items]
Number of offices	2,395	2,407	2,355
Franchise Group | Coldwell Banker®
Franchisor Disclosure [Line Items]
Number of offices	2,140	2,100	2,071
Franchise Group | Coldwell Banker Commercial®
Franchisor Disclosure [Line Items]
Number of offices	189	171	164
Franchise Group | Sotheby’s International Realty®
Franchisor Disclosure [Line Items]
Number of offices	1,071	1,035	986
Franchise Group | Better Homes and Gardens® Real Estate
Franchisor Disclosure [Line Items]
Number of offices	440	418	411
Franchise Group | Corcoran®
Franchisor Disclosure [Line Items]
Number of offices	96	82	122
Owned Brokerage Group
Franchisor Disclosure [Line Items]
Royalty expense | $	$ (301)	$ (358)	$ (393)
Marketing and Advertising Expense | $	$ (14)	$ (15)	$ (14)
Number of offices	623	679	675	620	673
Owned Brokerage Group | Coldwell Banker®
Franchisor Disclosure [Line Items]
Number of offices	551	606	605
Owned Brokerage Group | Sotheby’s International Realty®
Franchisor Disclosure [Line Items]
Number of offices	44	44	41
Owned Brokerage Group | Corcoran®
Franchisor Disclosure [Line Items]
Number of offices	28	29	29