Long-term Debt, Short-term Borrowings, and Capital Lease Obligations (Details) shares in Millions | 1 Months Ended | 3 Months Ended | 12 Months Ended | 21 Months Ended | | | | | |
Jun. 30, 2015USD ($) | Dec. 31, 2016USD ($)aircraft | Dec. 31, 2016USD ($)aircraftshares | Dec. 31, 2015USD ($)aircraftshares | Dec. 31, 2014USD ($) | Dec. 31, 2005aircraft | Mar. 30, 2014USD ($)aircraft | Apr. 30, 2013USD ($) | Jun. 30, 2009USD ($) | Nov. 30, 2004USD ($) | Mar. 31, 2004USD ($) |
Debt Instrument [Line Items] | | | | | | | | | | | |
Pledged Assets Not Separately Reported Flight Equipment | | $ 2,400,000,000 | $ 2,400,000,000 | | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months | | 185,000,000 | 185,000,000 | | | | | | | | |
Number Of Aircraft Finance By Pass through Certificate | aircraft | | | | | | 28 | | | | | |
Long-term Debt | | 1,255,000,000 | 1,255,000,000 | $ 1,688,000,000 | | | | | | | |
Long-term Debt, Fair Value | | 1,336,000,000 | 1,336,000,000 | 2,096,000,000 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Capital Leases (7) | | 140,000,000 | 140,000,000 | 155,000,000 | | | | | | | |
Total debt and capital lease obligations | | 1,395,000,000 | 1,395,000,000 | 1,843,000,000 | | | | | | | |
Less: current maturities | | (189,000,000) | (189,000,000) | (448,000,000) | | | | | | | |
Debt Acquisition Cost | | (11,000,000) | (11,000,000) | (16,000,000) | | | | | | | |
Long-term debt and capital lease obligations | | 1,195,000,000 | 1,195,000,000 | 1,379,000,000 | | | | | | | |
Capital Leases, Lessee Balance Sheet, Assets by Major Class, Accumulated Depreciation | | 56,000,000 | 56,000,000 | 48,000,000 | | | | | | | |
Capital Leases, Future Minimum Payments Due, Next Twelve Months | | 40,000,000 | 40,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Two Years | | 40,000,000 | 40,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Three Years | | 40,000,000 | 40,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Four Years | | 40,000,000 | 40,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Five Years | | 40,000,000 | 40,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due Thereafter | | 496,000,000 | 496,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments, Interest Included in Payments | | 27,000,000 | 27,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments | | 140,000,000 | 140,000,000 | | | | | | | | |
Capital Lease Obligations, Current | | 16,000,000 | 16,000,000 | | | | | | | | |
Capital Lease Obligations, Noncurrent | | 124,000,000 | 124,000,000 | | | | | | | | |
Prepayments of Debt, Amount | | | | 100,000,000 | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal in Year Two | | 193,000,000 | 193,000,000 | | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal in Year Three | | 215,000,000 | 215,000,000 | | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal in Year Four | | 179,000,000 | 179,000,000 | | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal in Year Five | | 164,000,000 | 164,000,000 | | | | | | | | |
Long-term Debt, Maturities, Repayments of Principal after Year Five | | $ 448,000,000 | 448,000,000 | | | | | | | | |
Interest Paid | | | $ 78,000,000 | $ 93,000,000 | $ 102,000,000 | | | | | | |
2004 Public Offering [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Face Amount | | | | | | | | | | $ 498,000,000 | $ 431,000,000 |
Public Debt Six Point Seven Five Percentage Series A Convertible Debentures Due In Two Zero Three Nine [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Face Amount | | | | | | | | | $ 115,000,000 | | |
Debt Instrument, Interest Rate, Stated Percentage | | 6.75% | 6.75% | | | | | | | | |
Public Debt Six Point Seven Five Percentage Series B Convertible Debentures Due In Two Zero Three Nine [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Face Amount | | | | | | | | | 86,000,000 | | |
Debt Instrument, Interest Rate, Stated Percentage | | 6.75% | 6.75% | | | | | | | | |
Floating rate equipment notes due through 2025 [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 4.20% | 4.20% | 3.70% | | | | | | | |
Secured Debt | | $ 173,000,000 | $ 173,000,000 | $ 193,000,000 | | | | | | | |
Public Debt Floating Rate Class G One Due Through Two Thousand Sixteen [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Debt | | 0 | 0 | 16,000,000 | | | | | | | |
Long-term Debt, Fair Value | | $ 0 | $ 0 | $ 16,000,000 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 0.00% | 0.00% | 4.40% | | | | | | | |
Secured Debt | | $ 0 | $ 0 | $ 16,000,000 | | | | | | | |
Public Debt Floating Rate Class G Two Due Two Thousand Sixteen Member | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Debt | | 0 | 0 | 185,000,000 | | | | | | | |
Long-term Debt, Fair Value | | $ 0 | $ 0 | $ 184,000,000 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 0.00% | 0.00% | 1.00% | | | | | | | |
Secured Debt | | $ 0 | $ 0 | $ 185,000,000 | | | | | | | |
Fixed Rate Equipment Notes Due Through Two Thousand Twenty Three [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Face Amount | | | | | | | $ 226,000,000 | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 4.50% | 4.50% | 4.50% | | | | | | | |
Secured Debt | | $ 189,000,000 | $ 189,000,000 | $ 201,000,000 | | | | | | | |
Fixed rate equipment notes, due through 2026 [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 5.50% | 5.50% | 5.50% | | | | | | | |
Secured Debt | | $ 850,000,000 | $ 850,000,000 | $ 964,000,000 | | | | | | | |
Public Debt Fixed rate special facility bonds, due through 2036 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Face Amount | | | | | | | | $ 42,000,000 | | | |
Long-term Debt | | 43,000,000 | 43,000,000 | 43,000,000 | | | | | | | |
Long-term Debt, Fair Value | | $ 45,000,000 | $ 45,000,000 | $ 45,000,000 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 4.90% | 4.90% | 4.90% | | | | | | | |
Secured Debt | | $ 43,000,000 | $ 43,000,000 | $ 43,000,000 | | | | | | | |
Debt Instrument, Net Amount | | | | | | | | 43,000,000 | | | |
Debt Instrument, Unamortized Premium | | | | | | | | $ 1,000,000 | | | |
Extinguishment of Debt, Amount | $ 32,000,000 | | | | | | | | | | |
Public Debt 6.75% convertible debentures due in 2039 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Interest Rate, Stated Percentage | | 6.75% | 6.75% | | | | | | | | |
Proceeds From Debentures Net Of Expenses And Escrow Deposit | | | | | | | | | $ 197,000,000 | | |
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares | | | 17.6 | | | | | | | | |
Long-term Debt | | $ 0 | $ 0 | 86,000,000 | | | | | | | |
Long-term Debt, Fair Value | | 0 | 0 | 405,000,000 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Unsecured Debt | | $ 0 | $ 0 | $ 86,000,000 | | | | | | | |
Debt Instrument, Frequency of Periodic Payment | | | semi-annually | | | | | | | | |
Public Debt 5.5% convertible debentures due in 2038 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Stock Issued During Period, Shares, Conversion of Convertible Securities | shares | | | | 15.2 | | | | | | | |
Capital Lease Obligations [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Weighted average interest rate | | 4.30% | 4.30% | 4.10% | | | | | | | |
Non Public Debt Fixed Rate Enhanced Equipment Notes Due Through Two Thousand And Twenty Three [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Debt | | $ 850,000,000 | $ 850,000,000 | $ 201,000,000 | | | | | | | |
Long-term Debt, Fair Value | | 915,000,000 | 915,000,000 | 209,000,000 | | | | | | | |
Non Public Debt Floating Rate Equipment Notes Due Through Two Thousand And Twenty Five [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Debt | | 173,000,000 | 173,000,000 | 193,000,000 | | | | | | | |
Long-term Debt, Fair Value | | 179,000,000 | $ 179,000,000 | 195,000,000 | | | | | | | |
Secured Debt [Member] | London Interbank Offered Rate (LIBOR) [Member] | Floating rate equipment notes due through 2025 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Description of Variable Rate Basis | | | LIBOR, plus a margin | | | | | | | | |
Enhanced Equipment Trust Certificate [Member] | 2004 Public Offering [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Long-term debt and capital lease obligations | | | | | | | $ 188,000,000 | | | | |
Repayments of Debt | | 185,000,000 | | | | | | | | | |
Fixed Rate Equipment Notes Due Through Two Thousand Twenty Three [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Debt Instrument, Frequency of Periodic Payment | | | semi-annually | | | | | | | | |
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Description of Variable Rate Basis | | | LIBOR plus a margin | | | | | | | | |
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Minimum [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Basis Spread on Variable Rate | | | 1.00% | | | | | | | | |
Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | Maximum [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Basis Spread on Variable Rate | | | 2.75% | | | | | | | | |
Morgan Stanley [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Line of Credit | | 0 | $ 0 | 0 | | | | | | | |
Line of Credit Facility, Current Borrowing Capacity | | 200,000,000 | $ 200,000,000 | | | | | | | | |
Morgan Stanley [Member] | London Interbank Offered Rate (LIBOR) [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Description of Variable Rate Basis | | | LIBOR, plus a margin | | | | | | | | |
Revolving Credit Facility and Letter of Credit Facility [Member] | CitiBank [Member] | Line of Credit [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Long-term Line of Credit | | 0 | $ 0 | $ 0 | | | | | | | |
Line of Credit Facility, Current Borrowing Capacity | | $ 400,000,000 | $ 400,000,000 | | | | | | | | |
Revolving Credit Facility and Letter of Credit Facility [Member] | CitiBank [Member] | Line of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Debt Instrument, Description of Variable Rate Basis | | | LIBOR, plus a margin | | | | | | | | |
A-320-200 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Capital Lease Obligations, Number of Aircraft | aircraft | | 4 | 4 | 4 | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Prepayment of Principal Balance, Number of Aircrafts | aircraft | | | | 10 | | | | | | | |
Prepayment of Principal Balance, Number of Aircraft Unencumbered | aircraft | | | | 4 | | | | | | | |
A-320-200 [Member] | Fixed Rate Equipment Notes Due Through Two Thousand Twenty Three [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Number of New Aircraft Held As Security | aircraft | | | | | | | 14 | | | | |
A-321-200 [Member] | | | | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | | | | |
Capital Lease Obligations, Number of Aircraft | aircraft | | 2 | 2 | 2 | | | | | | | |
Aircraft [Domain] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Capital Leases (7) | | $ 253,000,000 | $ 253,000,000 | $ 253,000,000 | | | | | | | |
Capital Leases, Future Minimum Payments Due, Next Twelve Months | | 23,000,000 | 23,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Two Years | | 23,000,000 | 23,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Three Years | | 23,000,000 | 23,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Four Years | | 35,000,000 | 35,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due in Five Years | | 39,000,000 | 39,000,000 | | | | | | | | |
Capital Leases, Future Minimum Payments Due Thereafter | | $ 24,000,000 | $ 24,000,000 | | | | | | | | |
A-320 [Member] | | | | | | | | | | | |
Long-term debt and capital lease obligations and the weighted average interest rate | | | | | | | | | | | |
Prepayment of Principal Balance, Number of Aircraft with Lower Principal Balance Outstanding | aircraft | | | | 6 | | | | | | | |