Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 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 September 30, 2016 and December 31, 2015 were as follows:

	September 30, 2016				December 31, 2015
	Carrying Value		Estimated Fair Value		Carrying Value		Estimated Fair Value		Fair value level hierarchy
	(in millions)
Senior long-term debt	$	460.1	$	477.4	$	484.2	$	477.8	Level 3
Junior long-term debt	48.9		50.5		54.3		54.6		Level 3
Class A enhanced equipment trust certificates	394.8		402.7		95.8		94.8		Level 2
Class B enhanced equipment trust certificates	104.5		106.1		25.0		25.2		Level 2
Total long-term debt	$	1,008.3	$	1,036.7	$	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 September 30, 2016
	Total		Level 1		Level 2		Level 3
	(in millions)
Cash and cash equivalents	$	825.9	$	825.9	$	—	$	—
Investment securities	$	100.1	$	100.1	$	—	$	—
Total assets	$	926.0	$	926.0	$	—	$	—
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	$	—	$	—	$	—	$	—