Long-Term Debt and Short-Term Borrowings, Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Oct. 08, 2019	Oct. 01, 2019	Jan. 31, 2019	Dec. 31, 2018
Long-term Debt [Abstract]
Long-term debt	$ 104,042				$ 95,908
Less discount on issuance of long-term debt	(192)				(204)
Less unamortized debt issuance costs	(2,815)				(2,346)
Less current maturities	(6,500)				(30)
Long-term portion	94,535				93,328
10.17% Senior Notes, Series A, due 2019 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				6,000
Interest rate	10.17%			10.17%
9.60% Senior Notes, Series B, due 2019 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				5,000
Interest rate	9.60%			9.60%
1.00% Pennvest Note, due 2019 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				30
Interest rate	1.00%
10.05% Senior Notes, Series C, due 2020 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 6,500				6,500
Interest rate	10.05%
8.43% Senior Notes, Series D, due 2022 [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 Refunding Bonds Series 2008A, due 2029 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 12,000				12,000
4.75% York County Industrial Development Authority Revenue Bonds, Series 2006, due 2036 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				10,500
Interest rate	4.75%	4.75%
3.00% PEDFA Exempt Facilities Revenue Refunding Bonds, Series A of 2019, due 2036 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 10,500				0
Interest rate	3.00%	3.00%
4.50% PEDFA Exempt Facilities Revenue Refunding Bonds, Series 2014, due 2038 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				14,870
Interest rate	4.50%	4.50%
3.10% PEDFA Exempt Facilities Revenue Refunding Bonds, Series B of 2019, due 2038 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 14,870				0
Interest rate	3.10%	3.10%
5.00% Monthly Senior Notes, Series 2010A, due 2040 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 0				15,000
Interest rate	5.00%		5.00%
3.23% Senior Notes, due 2040 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 15,000				0
Interest rate	3.23%		3.23%
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				10,000
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%
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%
4.54% Senior Notes, due 2049 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 20,000				0
Interest rate	4.54%			4.54%
Committed Line of Credit, due 2021 [Member]
Long-term Debt [Abstract]
Long-term debt	$ 7,672				$ 8,508