Fair Value Measurements (Details) - USD ($) $ in Millions |
9 Months Ended | ||
---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Dec. 31, 2017 |
|
Investment | |||
Unrealized loss on embedded derivative | $ 2 | $ 4 | |
Cash | 54 | $ 120 | |
Cash equivalents: | |||
Cash and cash equivalents, adjusted cost | 1,022 | 835 | |
Cash and cash equivalents, fair value disclosure | 1,022 | 835 | |
Nonqualified employee benefit trusts | |||
Cash equivalents: | |||
Available-for-sale securities, adjusted cost | 18 | 17 | |
Available-for-sale securities, gross unrealized gain | 2 | 2 | |
Available-for-sale securities, fair value | 20 | 19 | |
Other debt securities | |||
Cash equivalents: | |||
Cash equivalents, adjusted cost | 5 | 5 | |
Cash equivalents, fair value | 5 | 5 | |
U.S. and Canadian government obligations | |||
Cash equivalents: | |||
Cash equivalents, adjusted cost | 963 | 710 | |
Cash equivalents, fair value | $ 963 | $ 710 |