CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Accounts receivable
Allowance for customer accounts receivable	$ 1	$ 1
Allowance for other accounts receivable	$ 1	$ 1
Preferred stock
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	50,000,000	50,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Treasury stock
Treasury stock, shares held (less than) (in shares)	1,000,000	1,000,000
Class A Stock
Common stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (less than for Class B shares) (in shares)	550,000,000	550,000,000
Common stock, shares issued (less than for Class B shares) (in shares)	256,000,000	256,000,000
Common stock, shares outstanding (less than for Class B shares) (in shares)	255,000,000	256,000,000
Class B Stock
Common stock
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (less than for Class B shares) (in shares)	1,000,000	1,000,000
Common stock, shares issued (less than for Class B shares) (in shares)	1,000,000	1,000,000
Common stock, shares outstanding (less than for Class B shares) (in shares)	1,000,000	1,000,000