Long-Term Debt - Outstanding Long-Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Jun. 30, 2013	May 31, 2013	Dec. 31, 2012	Sep. 30, 2013 9.57% bond, due May 1, 2018 [Member]		Dec. 31, 2012 9.57% bond, due May 1, 2018 [Member]		Sep. 30, 2013 10.03% bond, due May 1, 2018 [Member]		Dec. 31, 2012 10.03% bond, due May 1, 2018 [Member]		Sep. 30, 2013 9.08% bond, due June 1, 2022 [Member]		Dec. 31, 2012 9.08% bond, due June 1, 2022 [Member]		Sep. 30, 2013 7.83% note, due January 1, 2015 [Member]	Dec. 31, 2012 7.83% note, due January 1, 2015 [Member]	Sep. 30, 2013 6.64% note, due October 31, 2017 [Member]	Dec. 31, 2012 6.64% note, due October 31, 2017 [Member]	Sep. 30, 2013 5.50% note, due October 12, 2020 [Member]	Dec. 31, 2012 5.50% note, due October 12, 2020 [Member]	Sep. 30, 2013 5.93% note, due October 31, 2023 [Member]	Dec. 31, 2012 5.93% note, due October 31, 2023 [Member]	Sep. 30, 2013 5.68% note, due June 30, 2026 [Member]	Dec. 31, 2012 5.68% note, due June 30, 2026 [Member]	Jun. 30, 2011 5.68% note, due June 30, 2026 [Member]	Sep. 30, 2013 6.43% note, due May 2, 2028 [Member]	May 02, 2013 6.43% note, due May 2, 2028 [Member]	Dec. 31, 2012 6.43% note, due May 2, 2028 [Member]	Sep. 30, 2013 8.25% due March 1, 2014 [Member]	Dec. 31, 2012 8.25% due March 1, 2014 [Member]	Sep. 30, 2013 Promissory note [Member]	Dec. 31, 2012 Promissory note [Member]
Debt Instrument [Line Items]
Total long-term debt		$ 108,500			$ 0	[1]	$ 5,444	[1]	$ 0	[1]	$ 2,994	[1]	$ 7,966	[1]	$ 7,962	[1]	$ 4,000	$ 4,000	$ 13,636	$ 13,636	$ 16,000	$ 16,000	$ 30,000	$ 30,000	$ 29,000	$ 29,000	$ 29,000	$ 7,000	$ 7,000	$ 0	$ 854	$ 942	$ 80	$ 125
Capital Lease Obligations	7,042		7,100	0
Total Long-term debt	115,578			110,103
Less: current maturities	(8,234)			(8,196)
Total long-term debt, net of current maturities	$ 107,344	$ 107,344		$ 101,907

[1] FPU secured first mortgage bonds are guaranteed by Chesapeake.