Indebtedness - Principal Payments Due on Long-Term Borrowings (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
2020	$ 0
2021	800
2022	500
2023	500
2024	500
Thereafter	3,303
Total principal payment	5,603	$ 5,722
4.50% 2012 Senior Notes, due 2022
Debt Instrument [Line Items]
2022	500
Total principal payment	500	500
4.875% 2013 Senior Notes, due 2024
Debt Instrument [Line Items]
2024	500
Thereafter	0
Total principal payment	500	500
5.25% 2014 Senior Notes (30-Year), due 2044
Debt Instrument [Line Items]
Thereafter	600
Total principal payment	$ 600	$ 600
Term of notes	30 years	30 years
1.75% 2015 Senior Notes, due 2027
Debt Instrument [Line Items]
Thereafter	$ 561
Total principal payment	561	$ 572
2.75% 2017 Senior Notes, due 2021
Debt Instrument [Line Items]
2021	500
Total principal payment	500
2.625% 2017 Senior Notes, due 2023
Debt Instrument [Line Items]
2023	500
Total principal payment	500	500
3.25% 2017 Senior Notes, due 2028
Debt Instrument [Line Items]
Thereafter	500
Total principal payment	500	500
3.25% 2018 Senior Notes, due 2021
Debt Instrument [Line Items]
2021	300
Total principal payment	300	300
4.25% 2018 Senior Notes, due 2029
Debt Instrument [Line Items]
Thereafter	400
Total principal payment	400	400
4.875% 2018 Senior Notes, due 2048
Debt Instrument [Line Items]
Thereafter	400
Total principal payment	400	$ 400
0.950% 2019 Senior Note, due 2030
Debt Instrument [Line Items]
Thereafter	842
Total principal payment	$ 842

Face (par) amount of debt instrument at time of issuance.

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