INVESTMENTS AND FAIR VALUE MEASUREMENT - SCHEDULE OF FINANCIAL ASSETS AND LIABILITIES MEASURED AT FAIR VALUE ON A RECURRING BASIS (Details) - Fair Value, Recurring - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Assets
Total financial assets	$ 3,603	$ 5,879
Liabilities
Total financial liabilities	1,929	1,834
Asset-backed securities
Assets
Investments	8	5
Commercial paper
Assets
Investments	19	14
Corporate bonds
Assets
Investments	12	7
Government bonds
Assets
Investments	1	1
User-held fractional shares
Assets
Other current assets	1,929	1,834
Equity securities - securities owned
Assets
Other current assets	10	14
Fractional share repurchase obligations
Liabilities
Fractional share repurchase obligations	1,929	1,834
Money market funds
Assets
Cash equivalents	1,624	4,004
Level 1
Assets
Total financial assets	3,564	5,853
Liabilities
Total financial liabilities	1,929	1,834
Level 1 | Asset-backed securities
Assets
Investments	0	0
Level 1 | Commercial paper
Assets
Investments	0	0
Level 1 | Corporate bonds
Assets
Investments	0	0
Level 1 | Government bonds
Assets
Investments	1	1
Level 1 | User-held fractional shares
Assets
Other current assets	1,929	1,834
Level 1 | Equity securities - securities owned
Assets
Other current assets	10	14
Level 1 | Fractional share repurchase obligations
Liabilities
Fractional share repurchase obligations	1,929	1,834
Level 1 | Money market funds
Assets
Cash equivalents	1,624	4,004
Level 2
Assets
Total financial assets	39	26
Liabilities
Total financial liabilities	0	0
Level 2 | Asset-backed securities
Assets
Investments	8	5
Level 2 | Commercial paper
Assets
Investments	19	14
Level 2 | Corporate bonds
Assets
Investments	12	7
Level 2 | Government bonds
Assets
Investments	0	0
Level 2 | User-held fractional shares
Assets
Other current assets	0	0
Level 2 | Equity securities - securities owned
Assets
Other current assets	0	0
Level 2 | Fractional share repurchase obligations
Liabilities
Fractional share repurchase obligations	0	0
Level 2 | Money market funds
Assets
Cash equivalents	0	0
Level 3
Assets
Total financial assets	0	0
Liabilities
Total financial liabilities	0	0
Level 3 | Asset-backed securities
Assets
Investments	0	0
Level 3 | Commercial paper
Assets
Investments	0	0
Level 3 | Corporate bonds
Assets
Investments	0	0
Level 3 | Government bonds
Assets
Investments	0
Level 3 | User-held fractional shares
Assets
Other current assets	0	0
Level 3 | Equity securities - securities owned
Assets
Other current assets	0	0
Level 3 | Fractional share repurchase obligations
Liabilities
Fractional share repurchase obligations	0	0
Level 3 | Money market funds
Assets
Cash equivalents	$ 0	$ 0