Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	$ (1,843)
Other comprehensive income (loss)	(429)	$ 107	$ (150)
Balance at end of the period	(2,272)	(1,843)
Net Effect of Exchange Rate Fluctuations
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(813)	(889)
Change before reclassifications	(267)	76
Other comprehensive income (loss)	(416)	76
Balance at end of the period	(1,229)	(813)	(889)
Change in Certain Derivative Instruments
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(14)	(18)
Change before reclassifications	(156)	(74)
Amounts reclassified from accumulated other comprehensive income (loss)	112	75
Translation effect	(2)	1
Tax effect	(1)	2
Other comprehensive income (loss)	(46)	4
Balance at end of the period	(60)	(14)	(18)
Employee Benefit Plans
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(1,016)	(1,061)
Change before reclassifications	(32)	(21)
Amounts reclassified from accumulated other comprehensive income (loss)	68	70
Translation effect	(9)	(7)
Tax effect	2	3
Other comprehensive income (loss)	33	45
Balance at end of the period	(983)	(1,016)	(1,061)
Accumulated Other Comprehensive Loss.
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Balance at beginning of the period	(1,843)	(1,968)
Change before reclassifications	(455)	(19)
Amounts reclassified from accumulated other comprehensive income (loss)	180	145
Translation effect	(11)	(6)
Tax effect	1	5
Other comprehensive income (loss)	(429)	125
Balance at end of the period	(2,272)	$ (1,843)	$ (1,968)
Australia And New Zealand ("ANZ") business | Net Effect of Exchange Rate Fluctuations
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Amounts reclassified from accumulated other comprehensive income (loss)	(149)
Australia And New Zealand ("ANZ") business | Change in Certain Derivative Instruments
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Amounts reclassified from accumulated other comprehensive income (loss)	1
Australia And New Zealand ("ANZ") business | Employee Benefit Plans
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Amounts reclassified from accumulated other comprehensive income (loss)	4
Australia And New Zealand ("ANZ") business | Accumulated Other Comprehensive Loss.
Increase (Decrease) Accumulated Other Comprehensive Loss, Net of Tax
Amounts reclassified from accumulated other comprehensive income (loss)	$ (144)