Debt (Tables)

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

Schedule of Long-term Debt Instruments

(Dollars in thousands)	2016			2015
Term loans, variable rate 2.50% to 3.00% due 2019 through 2026 and    fixed rate 2.95% to 4.64% due 2017 through 2024	$	349,500		$	322,000
Senior notes, 7.50% due 2019		150,000			150,000
Revenue bonds, 2.75% due 2024		65,735			108,335
Medium-term notes, 8.75% to 8.89%, due 2017 through 2022		22,250			27,250
Long-term principal		587,485			607,585
Interest rate swaps		247			581
Less debt issuance costs		(3,015	)		(3,037	)
Less unamortized discounts		(729	)		(1,248	)
Total long-term debt (includes current portion)		583,988			603,881
Less current portion of long-term debt		(11,032	)		(5,007	)
Long-term debt	$	572,956		$	598,874

Schedule of Maturities of Long-term Debt

Scheduled principal payments due on long-term debt as of December 31, 2016 are as follows:

(Dollars in thousands)
2017	$	11,000
2018		14,250
2019		190,000
2020		46,000
2021		40,000
Thereafter		286,235
Total	$	587,485