Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	$ 17,565	$ 34,781	$ 34,499	$ 35,013
Other comprehensive income (loss) before reclassifications			(164)	(116)
Amounts reclassified from accumulated other comprehensive income (loss)			33	21
Deferred taxes			(2)	(4)
Other comprehensive income (loss)	83	(115)	(133)	(99)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	29	(42)	(52)	(33)
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units			84	350
Less: Other adjustments				59
Ending Balance	17,249	34,436	17,249	34,436
Investment Securities, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			1	0
Ending Balance	0	0	0	0
Investment Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications			(2)	0
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Deferred taxes			0	0
Other comprehensive income (loss)			(2)	0
Investment Securities, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive income (loss) attributable to noncontrolling interests			(1)	1
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units			0	(1)
Less: Other adjustments				0
Foreign Currency Translation Adjustment, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(1,436)	(1,152)
Ending Balance	(1,570)	(1,530)	(1,570)	(1,530)
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications			(101)	(96)
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Deferred taxes			0	0
Other comprehensive income (loss)			(101)	(96)
Foreign Currency Translation Adjustments, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive income (loss) attributable to noncontrolling interests			(42)	(32)
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units			75	314
Less: Other adjustments				0
Cash Flow Hedges, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			6	(1)
Ending Balance	2	0	2	0
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications			(5)	2
Amounts reclassified from accumulated other comprehensive income (loss)			(2)	2
Deferred taxes			1	(1)
Other comprehensive income (loss)			(6)	3
Cash Flow Hedges, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive income (loss) attributable to noncontrolling interests			(2)	2
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units			0	0
Less: Other adjustments				0
Benefit Plans, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance			(207)	(66)
Ending Balance	(233)	(164)	(233)	(164)
Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications			(56)	(22)
Amounts reclassified from accumulated other comprehensive income (loss)			35	19
Deferred taxes			(3)	(3)
Other comprehensive income (loss)			(24)	(6)
Benefit Plans, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive income (loss) attributable to noncontrolling interests			(7)	(4)
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units			9	37
Less: Other adjustments				59
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning Balance	(1,771)	(1,271)	(1,636)	(1,219)
Other comprehensive income (loss)	54	(73)	(81)	(66)
Ending Balance	$ (1,801)	$ (1,694)	$ (1,801)	$ (1,694)