Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
Receivables, allowance for doubtful accounts	$ 6	$ 7
Aircraft fuel, spare parts and supplies, obsolescence allowance	396	354
Intangibles, accumulated amortization	$ 1,363	$ 1,313
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized	1,000,000,000	1,000,000,000
Common shares, outstanding	272,464,412	286,973,195
United Airlines, Inc.
Receivables, allowance for doubtful accounts	$ 6	$ 7
Aircraft fuel, spare parts and supplies, obsolescence allowance	396	354
Intangibles, accumulated amortization	$ 1,363	$ 1,313
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized	1,000	1,000
Common shares, issued	1,000	1,000
Common shares, outstanding	1,000	1,000