Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current Assets
Allowance for doubtful accounts	$ 0	$ 0
Other Assets
Accumulated Amortization	$ 87	$ 82
Stockholders' Equity
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	1,000	1,000
Common stock, shares issued (in shares)	935.51	935.51