Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Allowance for doubtful accounts receivable	$ 2	$ 1
Variable interest entities - assets	11,290	9,363
Variable interest entities - liabilities	$ 4,839	$ 3,777
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	239,589,639	201,290,458
Common stock, outstanding shares	239,386,877	201,198,381
Consolidated VIEs [Member]
Variable interest entities - assets	$ 242	$ 242
Variable interest entities - liabilities	$ 219	$ 217