SIGNIFICANT ACCOUNTING POLICIES - Textual (Details) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017 USD ($)		Mar. 31, 2018 USD ($) joint_venture		Mar. 31, 2017 USD ($)
Variable Interest Entity [Line Items]
Other equity investments			$ 1,351	[1]	$ 1,217	[1]	$ 1,440
Real estate held for production of income	[1]		390		52
Redeemable noncontrolling interest	[1]		626		1,024
Tax Cuts And Jobs Act Of 2017, Transition tax for accumulated foreign earnings income tax expense			$ 23
Variable Interest Entity, Not Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, unused commitments					758
Variable Interest Entity, Not Primary Beneficiary | Other Equity Investments
Variable Interest Entity [Line Items]
Variable Interest Entity, nonconsolidated net assets					163,426
Variable interest, maximum loss exposure					1,130
Variable Interest Entity, Not Primary Beneficiary | Insurance
Variable Interest Entity [Line Items]
Other equity investments					1,130
Variable Interest Entity, Not Primary Beneficiary | Investment Management
Variable Interest Entity [Line Items]
Variable Interest Entity, nonconsolidated net assets					83,900
Variable interest, maximum loss exposure					$ 8
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Number of consolidated real estate joint ventures | joint_venture					1
Variable interest entity, consolidated, assets					$ 36
Variable Interest Entity, Primary Beneficiary, Aggregated Disclosure
Variable Interest Entity [Line Items]
Real estate held for production of income					$ 16
Number of nonconsolidated real estate joint ventures | joint_venture					2
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, consolidated, assets					$ 2,447
Variable interest entity, nonconsolidated, liabilities					1,219
Redeemable noncontrolling interest					982
Voting Interest Entities Member | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Variable interest entity, consolidated, assets					135
Variable interest entity, nonconsolidated, liabilities					4
Noncontrolling interest in variable interest entity					$ 10
UNITED STATES
Variable Interest Entity [Line Items]
Amortization period, front-end load commissions			5 years 6 months
Non-US
Variable Interest Entity [Line Items]
Amortization period, front-end load commissions			4 years
Scenario, Forecast
Variable Interest Entity [Line Items]
Effective income tax rate		19.00%

[1] See Note 2 for details of balances with variable interest entities.