Other Financial Data - Schedule of Other Non-current Assets (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Other Financial Data [Abstract]
Investments	$ 58		$ 57
Taxes receivable	83		84
Cost to obtain contracts with customers (1)	144		0
Other	154		166
Total	$ 439	$ 452	$ 307