Consolidated Statements of Common Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Total
Balance (in shares) at Dec. 31, 2017	39,557,491
Balance at Dec. 31, 2017	$ 197,787	$ 343,450	$ 161,286	$ (5,631)	$ 696,892
Common Stock Issuances, Net of Expenses (in shares)	127,598
Common Stock Issuances, Net of Expenses	$ 638	(638)
Common Stock Retirements (in shares)	(58,495)
Common Stock Retirements	$ (292)	(2,117)			(2,409)
Net Income			26,215		26,215
Other Comprehensive Income (Loss)				(502)	(502)
Employee Stock Incentive Plan Expense		1,146			1,146
Common Dividends			(13,292)		(13,292)
Balance (in shares) at Mar. 31, 2018	39,626,594
Balance at Mar. 31, 2018	$ 198,133	341,841	174,209	(6,133)	708,050
Balance (in shares) at Dec. 31, 2018	39,664,884
Balance at Dec. 31, 2018	$ 198,324	344,250	190,433	(4,144)	728,863
Common Stock Issuances, Net of Expenses (in shares)	120,048
Common Stock Issuances, Net of Expenses	$ 601	(601)
Common Stock Retirements (in shares)	(55,224)
Common Stock Retirements	$ (276)	(2,454)			(2,730)
Net Income			26,324		26,324
Other Comprehensive Income (Loss)				168	168
ASU 2018-02 2017 TCJA Stranded Tax Transfer			784	(784)
Employee Stock Incentive Plan Expense		1,796			1,796
Common Dividends			(13,922)		(13,922)
Balance (in shares) at Mar. 31, 2019	39,729,708
Balance at Mar. 31, 2019	$ 198,649	$ 342,991	$ 203,619	$ (4,760)	$ 740,499