Defined Contribution 401(k) Plan (Details) $ in Millions	4 Months Ended	8 Months Ended	12 Months Ended
	Apr. 30, 2016	Dec. 31, 2016 defined_contribution_plan	Dec. 31, 2016 USD ($) defined_contribution_plan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, number of plans | defined_contribution_plan		3	3
Defined contribution 401(k) plan, requisite service period			60 days
Defined contribution 401(k) plan, requisite age			21 years
Defined contribution 401(k) plan, matching contributions made in period | $			$ 16.2	$ 12.5	$ 9.7
Employee Retirement Savings Plan | Flight Attendants and Dispatchers
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match	50.00%	100.00%
Employee Retirement Savings Plan | Other Employees
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			50.00%
Employee Retirement Savings Plan | Maximum | Flight Attendants and Dispatchers
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, maximum employer contribution percent of the employee’s annual compensation	6.00%	6.00%
Employee Retirement Savings Plan | Maximum | Other Employees
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, maximum employer contribution percent of the employee’s annual compensation			6.00%
Pilots’ Retirement Savings Plan
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			100.00%
Pilots’ Retirement Savings Plan | Maximum
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, maximum employer contribution percent of the employee’s annual compensation			9.00%
Puerto Rico Retirement Savings Plan | Pilots
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			100.00%
Puerto Rico Retirement Savings Plan | Other Employees
Defined Contribution Plan Disclosure [Line Items]
Defined contribution plan, employer matching contribution, percent of match			50.00%
Puerto Rico Retirement Savings Plan | Maximum | Pilots
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, maximum employer contribution percent of the employee’s annual compensation			9.00%
Puerto Rico Retirement Savings Plan | Maximum | Other Employees
Defined Contribution Plan Disclosure [Line Items]
Defined contribution 401(k) plan, maximum employer contribution percent of the employee’s annual compensation			6.00%