Fair Value of Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2018

Fair Value Disclosures [Abstract]

Schedule of carrying amounts and estimated fair values of long-term debt, excluding capital lease obligations, and input level to determine fair values

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

		September 30, 2018			December 31, 2017
	Input Level	Carrying Amount		Fair Value	Carrying Amount	Fair Value
		(Dollars in millions)
Liabilities—Long-term debt, excluding capital lease and other obligations	2	$	35,702	35,750	36,835	36,402