Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2018

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 at December 31, 2018 and December 31, 2017, were as follows:

	As of December 31,
	2018				2017
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value		Fair value level hierarchy
	(in millions)
Fixed-rate senior term loans	$	382.4	$	373.6	$	417.9	$	435.3	Level 3
Fixed-rate junior term loans	31.1		31.1		39.3		40.4		Level 3
Fixed-rate term loans	625.1		600.1		518.0		528.6		Level 3
2015-1 EETC Class A	378.6		374.8		408.6		420.9		Level 2
2015-1 EETC Class B	80.0		78.1		92.0		94.2		Level 2
2015-1 EETC Class C	109.5		107.9		—		—		Level 2
2017-1 EETC Class AA	242.5		228.8		37.5		37.4		Level 2
2017-1 EETC Class A	80.8		76.6		12.5		12.6		Level 2
2017-1 EETC Class B	83.7		79.1		13.8		13.8		Level 2
2017-1 EETC Class C	85.5		84.2		—		—		Level 2
Revolving credit facility	135.3		135.3		—		—		Level 3
Total long-term debt	$	2,234.5	$	2,169.6	$	1,539.6	$	1,583.2

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, 2018
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	1,004.7	$	1,004.7	$	—	$	—
Short-term investment securities	102.8		102.8		—		—
Total assets	$	1,107.5	$	1,107.5	$	—	$	—
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	$	—	$	—	$	—	$	—