PROPERTY, PLANT AND EQUIPMENT - Schedule of Real Estate Assets, Private Equity and Other (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	$ 53,005
Balance, end of period	67,294	$ 53,005
Costs
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	44,148
Balance, end of period	54,907	44,148
Accumulated Fair Value Changes
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	17,119
Balance, end of period	22,351	17,119
Accumulated depreciation
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	(8,262)
Balance, end of period	(9,964)	(8,262)
Real Estate
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	5,779	5,652
Additions, net of disposals and assets reclassified as held for sale	400	(212)
Acquisitions through business combinations	1,748	281
Foreign currency translation	(217)	280
Fair value changes	245	59
Depreciation expenses	(303)	(281)
Balance, end of period	7,652	5,779
Real Estate \| Costs
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	5,854	5,783
Additions, net of disposals and assets reclassified as held for sale	352	(502)
Acquisitions through business combinations	1,748	281
Foreign currency translation	(241)	292
Fair value changes	0	0
Depreciation expenses	0	0
Balance, end of period	7,713	5,854
Real Estate \| Accumulated Fair Value Changes
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	798	694
Additions, net of disposals and assets reclassified as held for sale	5	44
Acquisitions through business combinations	0	0
Foreign currency translation	(3)	1
Fair value changes	245	59
Depreciation expenses	0	0
Balance, end of period	1,045	798
Real Estate \| Accumulated depreciation
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	(873)	(825)
Additions, net of disposals and assets reclassified as held for sale	43	246
Acquisitions through business combinations	0	0
Foreign currency translation	27	(13)
Fair value changes	0	0
Depreciation expenses	(303)	(281)
Balance, end of period	(1,106)	(873)
Private Equity and Other
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	2,733	3,596
Additions, net of disposals and assets reclassified as held for sale	433	(1,178)
Acquisitions through business combinations	4,915	501
Foreign currency translation	(205)	180
Depreciation expenses	(536)	(358)
Impairment charges	(219)	(8)
Balance, end of period	7,121	2,733
Private Equity and Other \| Costs
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	4,050	5,268
Additions, net of disposals and assets reclassified as held for sale	360	(1,966)
Acquisitions through business combinations	4,915	501
Foreign currency translation	(298)	247
Depreciation expenses	0	0
Impairment charges	0	0
Balance, end of period	9,027	4,050
Private Equity and Other \| Accumulated Fair Value Changes
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	(231)
Balance, end of period	(434)	(231)
Private Equity and Other \| Accumulated Impairment
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	(231)	(243)
Additions, net of disposals and assets reclassified as held for sale	1	36
Acquisitions through business combinations	0	0
Foreign currency translation	15	(16)
Depreciation expenses	0	0
Impairment charges	(219)	(8)
Balance, end of period	(434)	(231)
Private Equity and Other \| Accumulated depreciation
Reconciliation of changes in property, plant and equipment [abstract]
Balance, beginning of period	(1,086)	(1,429)
Additions, net of disposals and assets reclassified as held for sale	72	752
Acquisitions through business combinations	0	0
Foreign currency translation	78	(51)
Depreciation expenses	(536)	(358)
Impairment charges	0	0
Balance, end of period	$ (1,472)	$ (1,086)

The increase in property, plant and equipment resulting from acquisitions through business combinations. [Refer: Business combinations [member]; Property, plant and equipment]

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The amount of additions to property, plant and equipment other than those acquired through business combinations. [Refer: Business combinations [member]; Property, plant and equipment]

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The amount of depreciation of property, plant and equipment. [Refer: Depreciation and amortisation expense; Property, plant and equipment]

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The amount of impairment loss recognised in profit or loss for property, plant and equipment. [Refer: Impairment loss recognised in profit or loss; Property, plant and equipment]

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The increase (decrease) in property, plant and equipment resulting from net exchange differences arising on the translation of the financial statements from the functional currency into a different presentation currency, including the translation of a foreign operation into the presentation currency of the reporting entity. [Refer: Property, plant and equipment]

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The amount of tangible assets that: (a) are held for use in the production or supply of goods or services, for rental to others, or for administrative purposes; and (b) are expected to be used during more than one period.

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The increase (decrease) in property, plant and equipment resulting from revaluations to fair value. [Refer: Property, plant and equipment; Revaluation surplus]

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