Reconciliation of Common Shareholders' Equity, Common Shares and Earnings Per Share - Reconciliation of common shares outstanding (Details 1)	9 Months Ended
	Sep. 30, 2016 shares
Schedule Of Common Stock Outstanding [Roll Forward]
Common Shares Outstanding, December 31, 2015	37,857,186
Issuances:
At-the-Market Offering	977,712
Automatic Dividend Reinvestment and Share Purchase Plan:
Dividends Reinvested	131,111
Cash Invested	79,494
Executive Stock Performance Awards (2013 and 2014 shares earned)	54,700
Employee Stock Purchase Plan:
Cash Invested	40,324
Dividends Reinvested	19,090
Employee Stock Ownership Plan	23,837
Restricted Stock Issued to Directors	23,200
Vesting of Restricted Stock Units	21,025
Directors Deferred Compensation	542
Retirements:
Shares Withheld for Individual Income Tax Requirements	(3,668)
Common Shares Outstanding, September 30, 2016	39,224,553