Reclassifications Out of Accumulated Other Comprehensive Loss - Reclassifications of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax benefit		$ 59	$ 60	$ 111	$ 111
Net income		171	152	326	297
Interest expense		$ 114	$ 100	211	$ 205
Reclassifications, net of tax	[1]			(6)
Past service liability
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1],[2]			0
Actuarial losses
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1],[2]			(1)
Amortization of defined benefit pension
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassifications, before tax	[1]			(1)
Income tax benefit	[1]			0
Reclassifications, net of tax	[1]			(1)
Reclassification out of Accumulated Other Comprehensive Income (loss) | Unrealized gains on available-for-sale securities
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net gain on securities	[1]			0
Income tax benefit	[1]			0
Net income	[1]			0
Reclassification out of Accumulated Other Comprehensive Income (loss) | Unrealized loss on cash flow hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income tax benefit	[1]			2
Net income	[1]			(5)
Interest expense	[1]			$ (7)

[1] Amounts in parentheses indicate expense items.

[2] See Note 8, “Pension and Other Post-Retirement Benefits,” for additional information.