Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Bonds repaid by meeting the special provision that allows representatives of deceased beneficial owners to request redemption prior to the stated maturity of all or part of their interest in the bonds.

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Amount of long-term debt, classified as current, that meet special redemption provisions that allow representatives of deceased beneficial owners to request redemption prior to the stated maturity of all or part of their interest in the bonds and have been tendered for redemption.

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Maximum amount that can be redeemed in the aggregate per year for bonds that contain special redemption provisions that allow representatives of deceased beneficial owners to request redemption prior to the stated maturity of all or part of their interest in the bonds. Limits the company's exposure to the amount of redemption of special provision cases per year.

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Maximum amount that can be redeemed per individual interest per year for bonds that contain special redemption provisions that allow representatives of deceased beneficial owners to request redemption prior to the stated maturity of all or part of their interest in the bonds. Limits the company's exposure to the amount of redemption of special provision cases per year.

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Long-Term Debt and Short-Term Borrowings, Fixed Rate Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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%
4.50% Pennsylvania Economic Development Financing Authority Exempt Facilities Revenue Refunding Bonds, Series 2014, due 2038 [Member]
Long-Term Debt [Abstract]
Interest rate	4.50%
Maximum amount that can be redeemed per individual interest per year	$ 25
Maximum amount that can be redeemed in the aggregate per year	300
Bonds tendered for redemption that meet special provisions	0
Bonds redeemed that meet special provisions	$ 0	$ 10	$ 0