Debt and Banking Arrangements (Tables)

12 Months Ended

Dec. 31, 2020

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments [Table Text Block]

Long-Term Debt

	December 31,
	2020		2019
	(Millions)
Transco:
7.08% Debentures due 2026	$	8	$	8
7.25% Debentures due 2026	200		200
7.85% Notes due 2026	1,000		1,000
4% Notes due 2028	400		400
3.25% Notes due 2030	700		—
5.4% Notes due 2041	375		375
4.45% Notes due 2042	400		400
4.6% Notes due 2048	600		600
3.95% Notes due 2050	500		—
Other financing obligation - Atlantic Sunrise	847		857
Other financing obligation - Dalton	257		259
Northwest Pipeline:
7.125% Debentures due 2025	85		85
4% Notes due 2027	500		500
Williams:
4.125% Notes due 2020	—		600
5.25% Notes due 2020	—		1,500
4% Notes due 2021	500		500
7.875% Notes due 2021	371		371
3.35% Notes due 2022	750		750
3.6% Notes due 2022	1,250		1,250
3.7% Notes due 2023	850		850
4.5% Notes due 2023	600		600
4.3% Notes due 2024	1,000		1,000
4.55% Notes due 2024	1,250		1,250
3.9% Notes due 2025	750		750
4% Notes due 2025	750		750
3.75% Notes due 2027	1,450		1,450
3.5% Notes due 2030	1,000		—
7.5% Debentures due 2031	339		339
7.75% Notes due 2031	252		252
8.75% Notes due 2032	445		445
6.3% Notes due 2040	1,250		1,250
5.8% Notes due 2043	400		400
5.4% Notes due 2044	500		500
5.75% Notes due 2044	650		650
4.9% Notes due 2045	500		500
5.1% Notes due 2045	1,000		1,000
4.85% Notes due 2048	800		800
Various — 7.7% to 10.25% Notes and Debentures due 2020 to 2027	3		24
Credit facility loans	—		—
Unamortized debt issuance costs	(125)		(119)
Net unamortized debt premium (discount)	(63)		(58)
Total long-term debt, including current portion	22,344		22,288
Long-term debt due within one year	(893)		(2,140)
Long-term debt	$	21,451	$	20,148

Schedule of Maturities of Long-term Debt [Table Text Block]

The following table presents aggregate minimum maturities of long-term debt and other financing obligations, excluding net unamortized debt premium (discount) and debt issuance costs, for each of the next five years: 

	December 31, 2020
	(Millions)
2021	$	894
2022	2,025
2023	1,477
2024	2,280
2025	1,617

Schedule of Line of Credit Facilities [Table Text Block]

Credit Facilities

	December 31, 2020
	Stated Capacity		Outstanding
	(Millions)
Long-term credit facility (1)	$	4,500	$	—
Letters of credit under certain bilateral bank agreements			15

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(1)    In managing our available liquidity, we do not expect a maximum outstanding amount in excess of the capacity of our credit facility inclusive of any outstanding amounts under our commercial paper program.