Long-Term Debt and Short-Term Borrowings (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015 USD ($) Bank	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Long-term Debt [Abstract]
Long-term debt	$ 87,542	$ 84,885
Less discount on issuance of long-term debt	(237)	0
Less current maturities	(44)	(43)
Long-term portion	87,261	84,842
Payments Due by Year [Abstract]
2016	44
2017	12,044
2018	44
2019	11,030
2020	6,500
Line of Credit Facility [Abstract]
Unsecured lines of credit aggregating amount	$ 29,000
Number of banks in which unsecured line of credit maintained | Bank	3
Debt Covenants and Restrictions [Abstract]
Maximum borrowing percentage of utility plant	60.00%
Base amount added to annual net income to determine restriction on dividends and stock acquisition	$ 1,500
Unsecured Line of Credit, First Note [Member]
Line of Credit Facility [Abstract]
Unsecured lines of credit aggregating amount	$ 13,000
Line of credit, maturity period	2 years
Line of credit, maturity date	May 01, 2017
Line of credit amount outstanding	$ 0	0
Unsecured Line of Credit, First Note [Member] | LIBOR [Member]
Line of Credit Facility [Abstract]
Basis for interest rate	1.20%
Unsecured Line of Credit, Second Note [Member]
Line of Credit Facility [Abstract]
Unsecured lines of credit aggregating amount	$ 11,000
Line of credit, maturity date	May 01, 2017
Line of credit compensating balance requirement	$ 0	0	$ 500
Line of credit amount outstanding	$ 0	0
Unsecured Line of Credit, Second Note [Member] | LIBOR [Member]
Line of Credit Facility [Abstract]
Basis for interest rate	1.25%
Unsecured Line of Credit, Third Note [Member]
Line of Credit Facility [Abstract]
Unsecured lines of credit aggregating amount	$ 5,000
Line of credit, maturity date	Jun. 01, 2016
Line of credit amount outstanding	$ 0	0
Unsecured Line of Credit, Third Note [Member] | LIBOR [Member]
Line of Credit Facility [Abstract]
Basis for interest rate	1.50%
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series A, due 2016, 4.05 Percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0	2,350
Interest rate	4.05%
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series A, due 2016, 5.00 Percent [Member
Long-term Debt [Abstract]
Long-term debt	$ 0	4,950
Interest rate	5.00%
Senior Notes, Series A, due 2019, 10.17 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 6,000	6,000
Interest rate	10.17%
Senior Notes, Series B, due 2019, 9.6 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 5,000	5,000
Interest rate	9.60%
Pennvest Loan, due 2019, 1.00 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 162	205
Interest rate	1.00%
Debt Covenants and Restrictions [Abstract]
Amount of receivables pledged as collateral	$ 800
Senior Notes, Series C, due 2020, 10.05 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 6,500	6,500
Interest rate	10.05%
Senior Notes, Series D, due 2022, 8.43 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 7,500	7,500
Interest rate	8.43%
Variable Rate Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds Series 2008A due 2029 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 12,000	$ 12,000
Payments Due by Year [Abstract]
2017	12,000
Long-Term Debt [Abstract]
Face value	$ 12,000
Variable interest rate, annual average	0.06%	0.07%
Variable interest rate, at year end	0.02%	0.05%
Period in which to reimburse bank for purchase price of tendered bonds that have not been remarketed	14 months
Variable Rate Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds Series 2008A due 2029 [Member] | Interest Rate Swap [Member]
Interest Rate Swap Agreement [Abstract]
Notional amount of swap	$ 12,000
Potential payment to counterparty	$ 2,683
Fixed interest rate	3.16%
Net payment rate on swap	3.06%	3.07%
Interest rate spread in basis points	(0.18%)	(0.05%)
Overall effective rate, including variable interest and swap payments	2.98%	3.11%
Variable Rate Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds Series 2008A due 2029 [Member] | LIBOR [Member] | Interest Rate Swap [Member]
Interest Rate Swap Agreement [Abstract]
Percentage of variable interest rate	59.00%
Variable Rate Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds Series 2008A due 2029 [Member] | Letter of Credit [Member]
Line of Credit Facility [Abstract]
Line of credit, maturity date	Jun. 30, 2017
Industrial Development Authority Revenue Bonds, series 2006, due 2036, 4.75 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 10,500	$ 10,500
Interest rate	4.75%
4.50% Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Refunding Bonds, Series 2014, due 2038 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 14,880	14,880
Interest rate	4.50%
Long-Term Debt [Abstract]
Special provision, amount to be redeemed per individual interest, per year, maximum	$ 25
Special provision, amount to be redeemed in the aggregate, per year, maximum	300
Special provision, repayment of bonds	0
Face value	14,880
Monthly Senior Notes, Series 2010A, due 2040, 5.00 percent [Member]
Long-term Debt [Abstract]
Long-term debt	$ 15,000	15,000
Interest rate	5.00%
4.00% - 4.50% York County Industrial Development Authority Exempt Facilities Revenue Bonds, Series 2015, due 2029 - 2045 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 10,000	$ 0
Long-Term Debt [Abstract]
Proceeds from debt, net of issuance costs	9,500
Face value	$ 10,000
4.00% - 4.50% York County Industrial Development Authority Exempt Facilities Revenue Bonds, Series 2015, due 2029 - 2045 [Member] | Maximum [Member]
Long-term Debt [Abstract]
Interest rate	4.50%
4.00% - 4.50% York County Industrial Development Authority Exempt Facilities Revenue Bonds, Series 2015, due 2029 - 2045 [Member] | Minimum [Member]
Long-term Debt [Abstract]
Interest rate	4.00%
Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Bonds, Series 2008B, due 2038, 6.00 percent [Member]
Long-term Debt [Abstract]
Interest rate		6.00%