Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 34,499	$ 35,013	$ 38,410
Other comprehensive income (loss) before reclassifications	(10)	(54)
Amounts reclassified from accumulated other comprehensive loss	47	27
Deferred taxes	6	19
Other comprehensive income (loss)	43	(8)	(573)
Less: Other comprehensive income (loss) attributable to noncontrolling interests	0	(1)	(343)
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units	185	350
Less: Other adjustments		60
Ending balance	18,242	34,499	35,013
Investment Securities, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	1	0
Ending balance	0	1	0
Investment Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	(2)	2
Amounts reclassified from accumulated other comprehensive loss	0	0
Deferred taxes	0	0
Other comprehensive income (loss)	(2)	2
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	0
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	(1,464)	(1,436)	(1,152)
Foreign Currency Translation Adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	175	53
Amounts reclassified from accumulated other comprehensive loss	0	0
Deferred taxes	0	0
Other comprehensive income (loss)	175	53
Foreign Currency Translation Adjustment, Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Less: Other comprehensive income (loss) attributable to noncontrolling interests	40	23
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units	163	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	3	6	(1)
Cash Flow Hedges
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	(2)	13
Amounts reclassified from accumulated other comprehensive loss	(4)	1
Deferred taxes	1	(2)
Other comprehensive income (loss)	(5)	12
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)	4
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units	0	0
Less: Other adjustments		1
Benefit Plans, Parent
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(207)	(66)
Ending balance	(317)	(207)	(66)
Benefit Plans
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Other comprehensive income (loss) before reclassifications	(181)	(122)
Amounts reclassified from accumulated other comprehensive loss	51	26
Deferred taxes	5	21
Other comprehensive income (loss)	(125)	(75)
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	(37)	(29)
Less: Reallocation of AOCL based on change in ownership of BHH LLC Units	22	36
Less: Other adjustments		59
Accumulated Other Comprehensive Loss
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(1,636)	(1,219)	(703)
Other comprehensive income (loss)	43	(7)	(230)
Ending balance	$ (1,778)	$ (1,636)	$ (1,219)