Long-term Debt (Tables)

6 Months Ended

Jun. 30, 2016

Debt Disclosure [Abstract]

Schedule of Long-term Debt

Long-term debt is comprised of the following:    

	As of				Three Months Ended June 30,				Six Months Ended June 30,
	June 30, 2016		December 31, 2015		2016		2015		2016		2015
	(in millions)				(weighted-average interest rates)
Fixed-rate senior term loans due through 2027	$	468.2	$	484.2	4.10	%	4.04	%	4.10	%	4.04	%
Fixed-rate junior term loans due through 2022	50.7		54.3		6.90	%	6.89	%	6.90	%	6.89	%
Fixed-rate class A enhanced equipment trust certificates due through 2028	333.3		95.8		4.03	%	N/A		4.03	%	N/A
Fixed-rate class B enhanced equipment trust certificates due through 2024	88.1		25.0		4.38	%	N/A		4.38	%	N/A
Long-term debt	$	940.3	$	659.3
Less current maturities	78.6		49.6
Less unamortized discounts, net	25.3		13.0
Total	$	836.4	$	596.7

Schedule of Maturities of Long-term Debt

At June 30, 2016, long-term debt principal payments for the next five years and thereafter were as follows:

	June 30, 2016
	(in millions)
remainder of 2016	$	44.7
2017	75.6
2018	74.9
2019	74.1
2020	72.6
2021 and thereafter	598.4
Total debt principal payments	$	940.3

Schedule of Interest Expense, Long-term Debt

Interest expense related to long-term debt consisted of the following:

	Three Months Ended June 30				Six Months Ended June 30,
	2016		2015		2016		2015
	(in thousands)
Senior term loans	$	4,964	$	3,426	$	10,012	$	5,620
Junior term loans	905		678		1,842		1,097
Class A enhanced equipment trust certificates	2,698		—		3,881		—
Class B enhanced equipment trust certificates	773		—		1,109		—
Commitment fees	30		—		65		—
Amortization of debt discounts	794		230		1,310		389
Total	$	10,164	$	4,334	$	18,219	$	7,106