Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2016

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 March 31, 2016 and December 31, 2015 were as follows:

	March 31, 2016				December 31, 2015
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value		Fair value level hierarchy
	(in millions)
Senior long-term debt	$	476.2	$	476.0	$	484.2	$	477.8	Level 3
Junior long-term debt	52.6		53.2		54.3		54.6		Level 3
Class A equipment trust certificates	154.2		154.2		95.8		94.8		Level 2
Class B equipment trust certificates	40.5		38.6		25.0		25.2		Level 2
Total long-term debt	$	723.5	$	722.0	$	659.3	$	652.4

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, 2016
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	902.8	$	902.8	$	—	$	—
Total assets	$	902.8	$	902.8	$	—	$	—
Total liabilities	$	—	$	—	$	—	$	—

	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	$	—	$	—	$	—	$	—