Debt and Other Obligations (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of long-term debt instruments

Long-term debt is comprised of the following:

	As of December 31,				Year Ended December 31,
	2016		2015		2016		2015
	(in millions)				(weighted-average interest rates)
Fixed-rate senior term loans due through 2027	$	451.9	$	484.2	4.10	%	4.10	%
Fixed-rate junior term loans due through 2022	47.1		54.3		6.90	%	6.90	%
Fixed-rate class A enhanced equipment trust certificates due through 2028	409.8		95.8		4.10	%	4.03	%
Fixed-rate class B enhanced equipment trust certificates due through 2024	103.6		25.0		4.45	%	4.37	%
Long-term debt	$	1,012.4	$	659.3
Less current maturities	84.4		49.6
Less unamortized discount, net	30.6		13.0
Total	$	897.4	$	596.7

Schedule of maturities of long-term debt

At December 31, 2016, long-term debt principal payments for the next five years and thereafter are as follows:

	December 31, 2016
	(in millions)
2017	$	88.9
2018	83.1
2019	81.5
2020	79.7
2021	78.2
2022 and thereafter	601.0
Total debt principal payments	$	1,012.4

Schedule of interest expense on long-term debt

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

	Year Ended December 31,
	2016		2015
	(in thousands)
Senior term loans	$	19,759	$	15,429
Junior term loans	3,568		2,997
Class A enhanced equipment trust certificates	11,509		494
Class B enhanced equipment trust certificates	3,243		140
Commitment fees	127		54
Amortization of deferred financing costs	3,435		1,165
Total	$	41,641	$	20,279