Debt - Schedule of Debt (Detail) - USD ($) $ in Millions	3 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Facility [Line Items]
Fair value adjustments related to interest rate swap fair value hedges	$ 18	$ 19
Unamortized issuance costs	(40)	(37)
Unamortized discount	(7)	(8)
Finance Lease, Liability	27	25
Total debt	5,748	5,924
Finance Lease, Liability, Current	4	3
Current debt	500	600
Long-term debt	5,244	5,321
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Proceeds from Debt, Net of Issuance Costs	494
Credit Agreement
Facility [Line Items]
Credit Facility	$ 125	200
Weighted-average variable interest rate	1.51%
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,400
Accounts Receivable Securitization Facility
Facility [Line Items]
Accounts Receivable Securitization Agreement	$ 350	350
Weighted-average variable interest rate	1.05%
Line of Credit Facility, Maximum Borrowing Capacity	$ 350
Accounts Recievable included in the Securitization Transaction	614
Senior Notes | Issued March 2010, interest at 5.350% payable semiannually, due March 2020
Facility [Line Items]
Senior Notes	$ 0	600
Debt interest rate percentage	5.35%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 0	600
Senior Notes | Issued September 2011, interest at 4.750% payable semiannually, due September 2021
Facility [Line Items]
Senior Notes	$ 500	500
Debt interest rate percentage	4.75%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 500	500
Senior Notes | Issued March 2012, interest at 4.950% payable semi-annually, due April 2022
Facility [Line Items]
Senior Notes	$ 350	350
Debt interest rate percentage	4.95%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 350	350
Senior Notes | Issued March 2013, interest at 3.875% payable semi-annually, due March 2023
Facility [Line Items]
Senior Notes	$ 500	500
Debt interest rate percentage	3.875%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 500	500
Senior Notes | Issued July 2018 and January 2019, interest at 5.375% payable semi-annually, due July 2025
Facility [Line Items]
Senior Notes	$ 825	825
Debt interest rate percentage	5.375%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 825	825
Senior Notes | Issued June 2020, interest at 5.625% payable semi-annually, due July 2027
Facility [Line Items]
Senior Notes	$ 500	0
Debt interest rate percentage	5.625%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 500	0
Senior Notes | Issued May 2019, interest at 5.125% payable semiannually, due May 2029
Facility [Line Items]
Senior Notes	$ 600	600
Debt interest rate percentage	5.125%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 600	600
Senior Notes | Issued August 2000, interest at 8.125% payable semi-annually, due August 2030
Facility [Line Items]
Senior Notes	$ 300	300
Debt interest rate percentage	8.125%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 300	300
Senior Notes | Issued October 2006, interest at 6.450% payable semi-annually, due November 2036
Facility [Line Items]
Senior Notes	$ 300	300
Debt interest rate percentage	6.45%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 300	300
Senior Notes | Issued September 2007, interest at 6.750% payable semi-annually, due September 2037
Facility [Line Items]
Senior Notes	$ 450	450
Debt interest rate percentage	6.75%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 450	450
Senior Notes | Issued March 2014, interest at 5.600% payable semi-annually, due April 2044
Facility [Line Items]
Senior Notes	$ 400	400
Debt interest rate percentage	5.60%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 400	400
Junior subordinated notes | Issued May 2013, interest at 5.850% payable semi-annually, due May 2043
Facility [Line Items]
Senior Notes	$ 550	550
Debt interest rate percentage	5.85%
Debt Instrument, Interest Rate, Stated Percentage [Abstract]
Debt Instrument, Face Amount	$ 550	$ 550