Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Allowance for doubtful accounts receivable	$ 2	$ 2
Variable interest entities - assets	11,277	11,290
Variable interest entities - liabilities	$ 5,694	$ 4,839
Common stock, par value (per share)	$ 0.01	$ 0.01
Common stock, authorized shares	6,000,000,000	6,000,000,000
Common stock, issued shares	235,721,204	239,589,639
Common stock, outstanding shares	235,427,598	239,386,877
Consolidated VIEs [Member]
Variable interest entities - assets	$ 237	$ 242
Variable interest entities - liabilities	$ 218	$ 219