Long-Term Debt - Outstanding Long-Term Debt (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Long-term Debt	$ 153,700	$ 161,500
Capital lease obligation	4,824	6,130
Long-term Debt and Capital Lease Obligations	158,491	167,595
Less: current maturities	(9,151)	(9,109)
Total long-term debt, net of current maturities	149,340	158,486
9.08% bond, due June 1, 2022
Debt Instrument [Line Items]
Long-term Debt	7,973	7,969
6.64% note, due October 31, 2017
Debt Instrument [Line Items]
Long-term Debt	5,456	8,182
5.50% note, due October 12, 2020
Debt Instrument [Line Items]
Long-term Debt	10,000	12,000
5.93% note, due October 31, 2023
Debt Instrument [Line Items]
Long-term Debt	24,000	27,000
5.68% note, due June 30, 2026
Debt Instrument [Line Items]
Long-term Debt	29,000	29,000
6.43% note, due May 2, 2028
Debt Instrument [Line Items]
Long-term Debt	7,000	7,000
3.73% note, due December 16, 2028
Debt Instrument [Line Items]
Long-term Debt	20,000	20,000
3.88% note, due May 15, 2029
Debt Instrument [Line Items]
Long-term Debt	50,000	50,000
Promissory note
Debt Instrument [Line Items]
Long-term Debt	$ 238	$ 314