CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Current Assets
Cash and cash equivalents	$ 194	$ 328
Marketable securities	1,427	1,252
Total cash and marketable securities	1,621	1,580
Receivables—less allowance for doubtful accounts of $1 and $1	341	302
Inventories and supplies—net	57	47
Prepaid expenses and other current assets	127	121
Total Current Assets	2,146	2,050
Property and Equipment
Aircraft and other flight equipment	7,559	6,947
Other property and equipment	1,222	1,103
Deposits for future flight equipment	494	545
Property and Equipment	9,275	8,595
Less accumulated depreciation and amortization	2,991	2,929
Total Property and Equipment—Net	6,284	5,666
Other Assets
Goodwill	1,943	1,934
Intangible assets—net	133	143
Other noncurrent assets	234	169
Total Other Assets	2,310	2,246
Total Assets	10,740	9,962
Current Liabilities
Accounts payable	120	92
Accrued wages, vacation and payroll taxes	418	397
Air traffic liability	937	849
Other accrued liabilities	918	878
Current portion of long-term debt	307	319
Total Current Liabilities	2,700	2,535
Long-Term Debt, Net of Current Portion	2,262	2,645
Other Liabilities and Credits
Deferred income taxes	454	463
Deferred revenue	699	640
Obligation for pension and postretirement medical benefits	453	331
Other liabilities	451	417
Total Other Liabilities and Credits	2,057	1,851
Commitments and Contingencies
Shareholders' Equity
Preferred stock, $0.01 par value, Authorized: 5,000,000 shares, none issued or outstanding	0	0
Common stock, $0.01 par value, Authorized: 400,000,000 shares, Issued: 2017 - 129,903,498 shares; 2016 - 129,189,634 shares, Outstanding: 2017 - 123,060,638 shares; 2016 - 123,328,051 shares	1	1
Capital in excess of par value	164	110
Treasury stock (common), at cost: 2017 - 6,842,860 shares; 2016 - 5,861,583 shares	(518)	(443)
Accumulated other comprehensive loss	(380)	(305)
Retained earnings	4,454	3,568
Shareholders' Equity Total	3,721	2,931
Total Liabilities and Shareholders' Equity	$ 10,740	$ 9,962