Long-Term Debt (Schedule Of Long-Term Debt) (Details) - USD ($) $ in Millions | 9 Months Ended | 12 Months Ended |
Sep. 30, 2021 | Dec. 31, 2020 |
Debt Instrument [Line Items] | | |
Total long-term debt | $ 10,617 | $ 9,327 |
Unamortized discount and debt issuance costs | (92) | (98) |
Less amount due currently | (2,172) | |
Long-term debt, less amounts due currently | 8,353 | 9,229 |
Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | 9,327 | 9,327 |
Unsecured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Variable rate unsecured long-term debt | 1,290 | |
4.10% Senior Notes Due June 1, 2022 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 400 | $ 400 |
Interest percentage | 4.10% | 4.10% |
Maturity date | Jun. 1, 2022 | Jun. 1, 2022 |
7.00% Debentures Due September 1, 2022 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 482 | $ 482 |
Interest percentage | 7.00% | 7.00% |
Maturity date | Sep. 1, 2022 | Sep. 1, 2022 |
2.75% Senior Notes due June 1, 2024 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 500 | $ 500 |
Interest percentage | 2.75% | 2.75% |
Maturity date | Jun. 1, 2024 | Jun. 1, 2024 |
2.95% Senior Notes Due April 1, 2025 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 350 | $ 350 |
Interest percentage | 2.95% | 2.95% |
Maturity date | Apr. 1, 2025 | Apr. 1, 2025 |
0.55% Senior Notes due October 1, 2025 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 450 | $ 450 |
Interest percentage | 0.55% | 0.55% |
Maturity date | Oct. 1, 2025 | Oct. 1, 2025 |
3.86% Senior Notes, Series A, due December 3, 2025 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 174 | $ 174 |
Interest percentage | 3.86% | 3.86% |
Maturity date | Dec. 3, 2025 | Dec. 3, 2025 |
3.86% Senior Notes, Series B, due January 14, 2026 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 38 | $ 38 |
Interest percentage | 3.86% | 3.86% |
Maturity date | Jan. 14, 2026 | Jan. 14, 2026 |
3.70% Senior Notes Due November 15, 2028 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 650 | $ 650 |
Interest percentage | 3.70% | 3.70% |
Maturity date | Nov. 15, 2028 | Nov. 15, 2028 |
5.75% Senior Notes Due March 15, 2029 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 318 | $ 318 |
Interest percentage | 5.75% | 5.75% |
Maturity date | Mar. 15, 2029 | Mar. 15, 2029 |
2.75% Senior Notes due May 15, 2030 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 400 | $ 400 |
Interest percentage | 2.75% | 2.75% |
Maturity date | May 15, 2030 | May 15, 2030 |
7.00% Senior Notes Due May 1, 2032 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 494 | $ 494 |
Interest percentage | 7.00% | 7.00% |
Maturity date | May 1, 2032 | May 1, 2032 |
7.25% Senior Notes Due January 15, 2033 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 323 | $ 323 |
Interest percentage | 7.25% | 7.25% |
Maturity date | Jan. 15, 2033 | Jan. 15, 2033 |
7.50% Senior Notes Due September 1, 2038 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 300 | $ 300 |
Interest percentage | 7.50% | 7.50% |
Maturity date | Sep. 1, 2038 | Sep. 1, 2038 |
5.25% Senior Notes Due September 30, 2040 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 475 | $ 475 |
Interest percentage | 5.25% | 5.25% |
Maturity date | Sep. 30, 2040 | Sep. 30, 2040 |
4.55% Senior Notes Due December 1, 2041 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 400 | $ 400 |
Interest percentage | 4.55% | 4.55% |
Maturity date | Dec. 1, 2041 | Dec. 1, 2041 |
5.30% Senior Notes Due June 1, 2042 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 348 | $ 348 |
Interest percentage | 5.30% | 5.30% |
Maturity date | Jun. 1, 2042 | Jun. 1, 2042 |
3.75% Senior Notes Due April 1, 2045 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 550 | $ 550 |
Interest percentage | 3.75% | 3.75% |
Maturity date | Apr. 1, 2045 | Apr. 1, 2045 |
3.80% Senior Notes Due September 30, 2047 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 325 | $ 325 |
Interest percentage | 3.80% | 3.80% |
Maturity date | Sep. 30, 2047 | Sep. 30, 2047 |
4.10% Senior Notes Due November 15, 2048 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 450 | $ 450 |
Interest percentage | 4.10% | 4.10% |
Maturity date | Nov. 15, 2048 | Nov. 15, 2048 |
3.80% Senior Notes, Due June 1, 2049 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 500 | $ 500 |
Interest percentage | 3.80% | 3.80% |
Maturity date | Jun. 1, 2049 | Jun. 1, 2049 |
3.10% Senior Notes, Due September 15, 2049 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 700 | $ 700 |
Interest percentage | 3.10% | 3.10% |
Maturity date | Sep. 15, 2049 | Sep. 15, 2049 |
3.70% Senior Notes Due May 15, 2050 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 400 | $ 400 |
Interest percentage | 3.70% | 3.70% |
Maturity date | May 15, 2050 | May 15, 2050 |
5.35% Senior Notes due October 1, 2052 [Member] | Secured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Fixed rate secured long-term debt | $ 300 | $ 300 |
Interest percentage | 5.35% | 5.35% |
Maturity date | Oct. 1, 2052 | Oct. 1, 2052 |
Term Loan Credit Agreement Maturing February 28, 2022 [Member] | Unsecured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Variable rate unsecured long-term debt | $ 300 | |
Maturity date | Feb. 28, 2022 | |
Term Loan Credit Agreement Maturing May 17, 2022 [Member] | Unsecured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Variable rate unsecured long-term debt | $ 450 | |
Maturity date | May 17, 2022 | |
Term Loan Credit Agreement Maturing August 15, 2022 [Member] | Unsecured Debt [Member] | | |
Debt Instrument [Line Items] | | |
Variable rate unsecured long-term debt | $ 540 | |
Maturity date | Aug. 15, 2022 | |