Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2015

Fair Value Disclosures [Abstract]

Long-term debt measured at fair value

The carrying amounts and estimated fair values of the Company's long-term debt, including current maturities, at December 31, 2015 and December 31, 2014, were as follows:

	As of December 31,
	2015				2014
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value		Fair value level hierarchy
	(in millions)
Senior long-term debt	$	484.2	$	477.8	$	132.0	$	132.0	Level 3
Junior long-term debt	54.3		54.6		16.0		16.1		Level 3
Class A equipment trust certificates	95.8		94.8		—		—		Level 2
Class B equipment trust certificates	25.0		25.2		—		—		Level 2
Total long-term debt	$	659.3	$	652.4	$	148.0	$	148.1

Assets and liabilities measured at fair value on a recurring basis

Assets and liabilities measured at gross fair value on a recurring basis are summarized below:

	Fair Value Measurements as of December 31, 2015
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	803.6	$	803.6	$	—	$	—
Total assets	$	803.6	$	803.6	$	—	$	—
Total liabilities	$	—	$	—	$	—	$	—

	Fair Value Measurements as of December 31, 2014
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	632.8	$	632.8	$	—	$	—
Jet fuel options	4.8		—		—		4.8
Total assets	$	637.6	$	632.8	$	—	$	4.8
Interest rate swaps	$	1.1	$	—	$	1.1	$	—
Total liabilities	$	1.1	$	—	$	1.1	$	—

Assets and liabilities measured at fair value on a recurring basis using significant unobservable inputs (level 3)

The following table presents the Company’s activity for assets and liabilities measured at gross fair value on a recurring basis using significant unobservable inputs (Level 3):

	Jet Fuel Options
	(in thousands)
Balance at January 1, 2013	$	265
Total realized or unrealized gains (losses) included in earnings, net	157
Purchases	—
Sales	—
Settlements, net	(422		)
Balance at December 31, 2013	—
Total realized or unrealized gains (losses) included in earnings, net	(4,876		)
Purchases	9,679
Sales	—
Settlements, net	—
Balance at December 31, 2014	4,803
Total realized or unrealized gains (losses) included in earnings, net	(6,700		)
Purchases	2,474
Sales	—
Settlements, net	(577		)
Balance at December 31, 2015	$	—