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Commitments and Contingencies - Airport Projects (Details) - USD ($) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2010 | Jun. 30, 2018 | Dec. 31, 2017
Airport Project [Line Items] |  |  |  |
Assets constructed for others |  |  | $ 1,664 | $ 1,543
Assets constructed for others, net |  |  | 1,553 | 1,448
Construction obligation |  |  | 1,613 | 1,390
Fort Lauderdale-Hollywood International Airport |  |  |  |
Airport Project [Line Items] |  |  |  |
Total Expected Cost Of Airport Project |  |  | 333 |
Assets constructed for others | [1] |  | 299 | 258
Assets constructed for others, net | [1],[2] |  | 295 | 256
Construction obligation | [1],[3] |  | 297 | 258
Los Angeles World Airport Terminal 1 |  |  |  |
Airport Project [Line Items] |  |  |  |
Total Expected Cost Of Airport Project |  |  | 526 |
Outstanding remaining guaranteed obligation |  |  | 127 |
Total Expected Cost Of Airport Project Nonproprietary |  |  | 510 |
Assets constructed for others | [1] |  | 463 | 433
Assets constructed for others, net | [1],[2] |  | 443 | 417
Construction obligation | [1],[3] |  | 459 | 433
Los Angeles World Airport Terminal 1.5 |  |  |  |
Airport Project [Line Items] |  |  |  |
Total Expected Cost Of Airport Project |  |  | 479 |
Outstanding remaining guaranteed obligation |  |  | 61 |
Assets constructed for others | [1] |  | 54 | 31
Assets constructed for others, net | [1],[2] |  | 54 | 31
Construction obligation | [1],[3] |  | 54 | 31
Dallas Love Field Terminal |  |  |  |
Airport Project [Line Items] |  |  |  |
Assets constructed for others |  |  | 544 | 543
Assets constructed for others, net | [2] |  | 467 | 474
Construction obligation | [3] |  | 509 | 516
Municipal bonds issued |  | $ 456 |  |
Municipal bonds principal remaining |  |  | 424 |
Dallas Love Field Parking Garage |  |  |  |
Airport Project [Line Items] |  |  |  |
Assets constructed for others | [1] |  | 178 | 152
Assets constructed for others, net | [1],[2] |  | 178 | 152
Construction obligation | [1],[3] |  | 178 | 152
Houston Hobby Airport |  |  |  |
Airport Project [Line Items] |  |  |  |
Airport Cost |  |  | 150 |
Reimbursement for Airport Project |  |  | 116 |
Assets constructed for others |  |  | 126 | 126
Assets constructed for others, net | [2] |  | 116 | 118
Construction obligation | [3] |  | $ 116 | $ 0
[1] | Projects still in progress.
[2] | Net of accumulated depreciation.
[3] | Construction obligation will be reduced through future facility rent payments. These future payments are not fixed per the lease agreement, but are variable and fluctuate based on various market and other factors outside the control of the Company.

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