| **Quarterly Financial Data (Unaudited) (Details) (USD $)In Thousands, except Per Share data, unless otherwise specified** | 3 Months Ended | 12 Months Ended |
|---------------------------------------------------------------------------------------------------------------------------|----------------|-----------------|
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| **Quarterly Financial Data (Unaudited) [Abstract]**                                                                       |           |            |   |   |   |   |   |   |   |   |   |
| Revenue                                                                                                                   | $ 1,180,369    | $ 1,185,278     | $ 1,190,533 | $ 1,205,396 | $ 1,232,553 | $ 1,252,469 | $ 1,258,777 | $ 1,268,054 | $ 4,761,576 | $ 5,011,853 | $ 5,243,043 |
| Operating income                                                                                                          | 257,569        | 206,172         | 266,156 | 250,824 | 235,730 | 275,196 | 267,784 | 208,458 | 980,721 | 987,168 | 899,621 |
| Net income (loss) attributable to common shareholders of Frontier                                                         | $ 67,755       | $ 35,400        | $ (38,460) | $ 48,140 | $ 24,879 | $ 67,000 | $ 17,989 | $ 26,768 | $ 112,835 | $ 136,636 | $ 149,614 |
| Basic net income (loss) per common share attributable to common shareholders of Frontier                                  | $ 0.07         | $ 0.04          | $ (0.04) | $ 0.05 | $ 0.02 | $ 0.07 | $ 0.02 | $ 0.03 | $ 0.11 | $ 0.14 | $ 0.15 |

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| - Definition
The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.
+ References
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|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.
+ References
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| - Definition
The net result for the period of deducting operating expenses from operating revenues.
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No definition available.
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|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).
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