Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

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 capital lease and other obligations, as well as the input level used to determine the fair values indicated below:

		June 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	$	10,696	10,413	10,711	10,528