Postretirement Benefits - Asset Allocation (Details) - Employee pension plan - Qualified Plan - Funded Plan	Dec. 31, 2021	Dec. 31, 2020
Target asset allocation for the portfolio:
Total plan assets	100.00%	100.00%
Actual asset allocation for the portfolio:
Total plan assets	100.00%	100.00%
Total equity securities
Target asset allocation for the portfolio:
Total plan assets	45.00%	45.00%
Actual asset allocation for the portfolio:
Total plan assets	45.00%	46.00%
U.S. equity securities
Target asset allocation for the portfolio:
Total plan assets	27.00%	27.00%
Actual asset allocation for the portfolio:
Total plan assets	27.00%	28.00%
U.S. small capitalization core equity
Target asset allocation for the portfolio:
Total plan assets	21.00%
U.S. equity index
Target asset allocation for the portfolio:
Total plan assets	79.00%
Non-U.S. equity securities
Target asset allocation for the portfolio:
Total plan assets	18.00%	18.00%
Actual asset allocation for the portfolio:
Total plan assets	18.00%	18.00%
International small capitalization risk controlled equity
Target asset allocation for the portfolio:
Total plan assets	11.00%
International emerging markets equity
Target asset allocation for the portfolio:
Total plan assets	20.00%
International risk controlled equity
Target asset allocation for the portfolio:
Total plan assets	69.00%
Debt securities
Target asset allocation for the portfolio:
Total plan assets	54.00%	54.00%
Actual asset allocation for the portfolio:
Total plan assets	54.00%	53.00%
U.S. Treasury Strips
Target asset allocation for the portfolio:
Total plan assets	34.00%
U.S. corporate bonds with an emphasis on long duration bonds rated A or better
Target asset allocation for the portfolio:
Total plan assets	66.00%
Other
Target asset allocation for the portfolio:
Total plan assets	1.00%	1.00%
Actual asset allocation for the portfolio:
Total plan assets	1.00%	1.00%