Statements of Net Proceeds From All Sources (Equity) (Parentheticals) - USD ($)	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
AOCI Attributable to Parent [Member]
Periodic pension costs, income taxes	$ 155,800	$ 55,940	$ (405,739)
Net Proceeds From All Sources [Member]
Dividends paid - per Sub-share (in dollars per share)	$ 0.31	$ 0.29	$ 0.27

Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss) for net transition asset (obligation) related to pension and other postretirement benefit plans.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e689-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=66004124&loc=d3e640-108580

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration