Accumulated Other Comprehensive Loss - Changes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
AOCI roll forward
Beginning balance	$ 6,276	$ 6,042	$ 5,320
Other comprehensive income (loss), net of tax	79	(90)	88
Ending balance	7,070	6,276	6,042
Accumulated Other Comprehensive Loss [Member]
AOCI roll forward
Beginning balance	(87)	8	(80)
Other comprehensive income (loss) before reclassifications, net of tax	72	(98)	82
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	7	8	6
Other comprehensive income (loss), net of tax	79	(90)	88
Ending balance	(8)	(87)	8
Accumulated Other Comprehensive Loss [Member] | Accounting Standards Update 2018-02 [Member]
AOCI roll forward
Adoption of new accounting standard		(5)
Derivative Instruments [Member]
AOCI roll forward
Beginning balance	(32)	(33)	(40)
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	8	8	7
Other comprehensive income (loss), net of tax	8	8	7
Ending balance	(24)	(32)	(33)
Derivative Instruments [Member] | Accounting Standards Update 2018-02 [Member]
AOCI roll forward
Adoption of new accounting standard		(7)
Available for sale Securities [Member]
AOCI roll forward
Beginning balance	23	15	13
Other comprehensive income (loss) before reclassifications, net of tax	15	5	3
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax			(1)
Other comprehensive income (loss), net of tax	15	5	2
Ending balance	38	23	15
Available for sale Securities [Member] | Accounting Standards Update 2018-02 [Member]
AOCI roll forward
Adoption of new accounting standard		3
Foreign Currency Translation Adjustments [Member]
AOCI roll forward
Beginning balance	(76)	29	(47)
Other comprehensive income (loss) before reclassifications, net of tax	55	(105)	76
Other comprehensive income (loss), net of tax	55	(105)	76
Ending balance	(21)	(76)	29
Post - Retirement Benefit Obligation [Member]
AOCI roll forward
Beginning balance	(2)	(3)	(6)
Other comprehensive income (loss) before reclassifications, net of tax	2	2	3
Amounts reclassified from accumulated other comprehensive (income) loss, net of tax	(1)
Other comprehensive income (loss), net of tax	1	2	3
Ending balance	$ (1)	(2)	$ (3)
Post - Retirement Benefit Obligation [Member] | Accounting Standards Update 2018-02 [Member]
AOCI roll forward
Adoption of new accounting standard		$ (1)