SIGNIFICANT ACCOUNTING POLICIES - Accounting and Consolidation of Variable Interest Entities (VIEs) (Details) $ in Millions	Dec. 31, 2020 USD ($) joint_venture	Dec. 31, 2019 USD ($) joint_venture
Variable Interest Entity [Line Items]
Assets	$ 251,294	$ 227,952
Consolidated Variable Interest Entities
Variable Interest Entity [Line Items]
Number of consolidated real estate joint ventures | joint_venture	1	1
Assets		$ 32
Non-consolidated Vairable Interest Entities
Variable Interest Entity [Line Items]
Assets	$ 165,800	160,200
Investment assets	1,300	1,100
Variable interest, maximum loss exposure	1,300	1,100
Unfunded commitments	$ 1,200	$ 1,100