Debt and Credit Agreements - Schedule of Senior Unsecured Notes Issued (Details) - Senior Notes - USD ($)	1 Months Ended
	Sep. 30, 2014	Dec. 31, 2010	Jul. 31, 2008	Oct. 07, 2021	Oct. 01, 2021
Debt Instrument [Line Items]
Principal (In millions)				$ 1,800,000,000	$ 2,000,000,000
6.51% weighted-average private placement senior notes
Debt Instrument [Line Items]
Principal (In millions)			$ 425,000,000
6.51% weighted-average private placement senior notes | Tranche 1
Debt Instrument [Line Items]
Principal (In millions)			$ 245,000,000
Term			10 years
Coupon			6.44%
6.51% weighted-average private placement senior notes | Tranche 2
Debt Instrument [Line Items]
Principal (In millions)			$ 100,000,000
Term			12 years
Coupon			6.54%
6.51% weighted-average private placement senior notes | Tranche 3
Debt Instrument [Line Items]
Principal (In millions)			$ 80,000,000
Term			15 years
Coupon			6.69%
5.58% weighted-average private placement senior notes
Debt Instrument [Line Items]
Principal (In millions)		$ 175,000,000
5.58% weighted-average private placement senior notes | Tranche 1
Debt Instrument [Line Items]
Principal (In millions)		$ 88,000,000
Term		10 years
Coupon		5.42%
5.58% weighted-average private placement senior notes | Tranche 2
Debt Instrument [Line Items]
Principal (In millions)		$ 25,000,000
Term		12 years
Coupon		5.59%
5.58% weighted-average private placement senior notes | Tranche 3
Debt Instrument [Line Items]
Principal (In millions)		$ 62,000,000
Term		15 years
Coupon		5.80%
3.65% weighted-average private placement senior notes
Debt Instrument [Line Items]
Principal (In millions)	$ 925,000,000
3.65% weighted-average private placement senior notes | Tranche 1
Debt Instrument [Line Items]
Principal (In millions)	$ 100,000,000
Term	7 years
Coupon	3.24%
3.65% weighted-average private placement senior notes | Tranche 2
Debt Instrument [Line Items]
Principal (In millions)	$ 575,000,000
Term	10 years
Coupon	3.67%
3.65% weighted-average private placement senior notes | Tranche 3
Debt Instrument [Line Items]
Principal (In millions)	$ 250,000,000
Term	12 years
Coupon	3.77%