Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2020

Fair Value Disclosures [Abstract]

Fair value measurement inputs and valuation techniques

The three input levels in the hierarchy of fair value measurements are defined by the FASB generally as follows:

Input Level	Description of Input
Level 1	Observable inputs such as quoted market prices in active markets.
Level 2	Inputs other than quoted prices in active markets that are either directly or indirectly observable.
Level 3	Unobservable inputs in which little or no market data exists.

Schedule of fair value of liabilities measured on a recurring basis

The following table presents the carrying amounts and estimated fair values of our long-term debt, excluding finance leases, as well as the input level used to determine the fair values indicated below:

		As of December 31,
		2020			2019
	Input Level	Carrying Amount		Fair Value	Carrying Amount	Fair Value
		(Dollars in million)
Liabilities-Long-term debt, excluding finance leases	2	$	10,132	10,340	10,196	10,244