Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2015

Fair Value Disclosures [Abstract]

Fair Value, Liabilities Measured on Recurring and Nonrecurring Basis [Table Text Block]

The carrying amounts and estimated fair values of our long-term debt at March 31, 2015 were as follows:

	Carrying Value		Estimated Fair Value
	(in millions)
Senior long-term debt	$	298.9	$	298.9
Junior long-term debt	31.5		32.0
Total long-term debt	$	330.4	$	330.9

Schedule of 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 March 31, 2015
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	741.6	$	741.6	$	—	$	—
Jet fuel options	2.5		—		—		2.5
Total assets	$	744.1	$	741.6	$	—	$	2.5
Interest rate swaps	$	3.7	$	—	$	3.7	$	—
Total liabilities	$	3.7	$	—	$	3.7	$	—

	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	$	—

Schedule of 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 Option Activity for the Three Months Ended March 31, 2015
	(in millions)
Balance at December 31, 2014	$	4.8
Total realized or unrealized gains (losses) included in earnings, net	(4.3		)
Purchases	2.1
Sales	—
Settlements, net	(0.1		)
Balance at March 31, 2015	$	2.5