Debt (Tables)

12 Months Ended

Dec. 31, 2014

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

The following table presents our long-term debt as of December 31:

(Dollars in thousands)	2014			2013
Term loans, variable rate 1.88% to 2.13% due 2019 through 2021 and fixed rate 2.95% to 4.64% due 2017 through 2024	$	322,000		$	12,000
Senior Notes, 7.50%, due 2019	150,000			150,000
Revenue bonds, 5.90% to 6.95%, due 2024 and 2026	108,335			108,335
Debentures, 6.95%, due 2015	22,500			22,500
Medium-term notes, 8.75% to 8.89%, due 2016 through 2022	27,250			27,250
	630,085			320,085
Interest rate swaps	793			1,830
Less unamortized discounts	(1,535		)	(1,823		)
	629,343			320,092
Less current portion	(22,870		)	—
Long-term debt	$	606,473		$	320,092

Schedule of Maturities of Long-term Debt

Scheduled principal payments due on long-term debt during each of the five years subsequent to December 31, 2014, are as follows:

(Dollars in thousands)
2015	$	22,500
2016	5,000
2017	11,000
2018	14,250
2019	190,000