Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2018

Fair Value Disclosures [Abstract]

Carrying amount and estimated fair value, long-term debt

The carrying amounts and estimated fair values of the Company's long-term debt at June 30, 2018 and December 31, 2017 were as follows:

	June 30, 2018				December 31, 2017				Fair Value Level Hierarchy
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value
	(in millions)
Senior term loans	$	400.3	$	400.9	$	417.9	$	435.3	Level 3
Junior term loans	35.3		35.6		39.3		40.4		Level 3
Fixed-rate loans	502.0		489.5		518.0		528.6		Level 3
2015-1 EETC Class A	393.6		394.8		408.6		420.9		Level 2
2015-1 EETC Class B	84.0		84.6		92.0		94.2		Level 2
2015-1 EETC Class C	115.2		114.9		—		—		Level 2
2017-1 EETC Class AA	190.0		184.8		37.5		37.4		Level 2
2017-1 EETC Class A	63.3		61.3		12.5		12.6		Level 2
2017-1 EETC Class B	70.0		68.2		13.8		13.8		Level 2
2017-1 EETC Class C	65.7		65.5		—		—		Level 2
Total long-term debt	$	1,919.4	$	1,900.1	$	1,539.6	$	1,583.2

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 June 30, 2018
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	812.4	$	812.4	$	—	$	—
Short-term investment securities	101.7		101.7		—		—
Total assets	$	914.1	$	914.1	$	—	$	—
Total liabilities	$	—	$	—	$	—	$	—

	Fair Value Measurements as of December 31, 2017
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	800.8	$	800.8	$	—	$	—
Short-term investment securities	100.9		100.9		—		—
Total assets	$	901.7	$	901.7	$	—	$	—
Total liabilities	$	—	$	—	$	—	$	—