CONSOLIDATED BALANCE SHEETS - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Current Assets
Cash and cash equivalents	$ 328	$ 73
Marketable securities	1,252	1,255
Total cash and marketable securities	1,580	1,328
Receivables—less allowance for doubtful accounts of $1 and $1	302	212
Inventories and supplies—net	47	51
Prepaid expenses and other current assets	121	72
Total Current Assets	2,050	1,663
Property and Equipment
Aircraft and other flight equipment	6,947	5,690
Other property and equipment	1,103	955
Deposits for future flight equipment	545	771
Property and Equipment	8,595	7,416
Less accumulated depreciation and amortization	2,929	2,614
Total Property and Equipment—Net	5,666	4,802
Other Assets [Abstract]
Goodwill	1,934	0
Intangible assets	143	0
Other noncurrent assets	169	65
Total Other Assets	2,246	65
Total Assets	9,962	6,530
Current Liabilities
Accounts payable	92	63
Accrued wages, vacation and payroll taxes	397	298
Other accrued liabilities	878	661
Air traffic liability	849	669
Current portion of long-term debt	319	114
Total Current Liabilities	2,535	1,805
Long-Term Debt, Net of Current Portion	2,645	569
Other Liabilities and Credits
Deferred income taxes	463	682
Deferred revenue	640	431
Obligation for pension and postretirement medical benefits	331	270
Other liabilities	417	362
Other Liabilities and Credits Totals	1,851	1,745
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: 200,000,000 shares, Issued: 2016 - 129,189,634 shares; 2015 - 128,442,099 shares, Outstanding: 2016 - 123,328,051 shares; 2015 - 125,175,325 shares	1	1
Capital in excess of par value	110	73
Treasury stock (common), at cost: 2016 - 5,861,583 shares; 2015 - 3,266,774 shares	(443)	(250)
Accumulated other comprehensive loss	(305)	(303)
Retained earnings	3,568	2,890
Shareholders' Equity Total	2,931	2,411
Total Liabilities and Shareholders' Equity	$ 9,962	$ 6,530