Debt (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Total long-term debt	$ 84,964	$ 84,975
Less current maturities	(42)	(42)
Long-term portion	84,922	84,933
Unsecured lines of credit aggregating amount	29,000
Number of banks in wich unsecured line of credit maintained	3
Demand deposit requirement, minimum	500	500
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series A, due 2016, 4.05 Percent [Member]
Debt Instrument [Line Items]
Total long-term debt	2,350	2,350
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series A, due 2016, 5.00 Percent [Member]
Debt Instrument [Line Items]
Total long-term debt	4,950	4,950
Senior Notes, Series A, due 2019, 10.17 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	6,000	6,000
Senior Notes, Series B, due 2019, 9.6 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	5,000	5,000
Pennvest Loan, due 2019, 1.00 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	279	290
Senior Notes, Series C, due 2020, 10.05 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	6,500	6,500
Senior Notes, Series D, due 2022, 8.43 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	7,500	7,500
Variable Rate Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds Series 2008A due 2029 [Member]
Debt Instrument [Line Items]
Total long-term debt	12,000	12,000
Industrial Development Authority Revenue Bonds, series 2006, due 2036, 4.75 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	10,500	10,500
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series 2008B, due 2038, 6.00 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	14,885	14,885
Monthly Senior Notes, Series 2010A, due 2040, 5.00 percent [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 15,000	$ 15,000