Subsequent Events Subsequent Events (Narrative) (Details) $ / shares in Units, $ in Millions		1 Months Ended
	Apr. 03, 2017 USD ($) a wells	Apr. 21, 2017 USD ($) shares	Apr. 04, 2017 USD ($) $ / shares	Mar. 31, 2017 $ / shares shares	Dec. 31, 2016 $ / shares shares
Subsequent Event [Line Items]
Common stock, par value | $ / shares				$ 0.20	$ 0.20
Common stock, shares issued | shares				52,018,042	51,494,318
At-the-market offering [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Common stock, par value | $ / shares			$ 0.20
Aggregate Offering Price			$ 100.0
Commission of the gross sales price by share paid percentage			2.00%
Common stock, shares issued | shares		770,660
Stock offering proceeds		$ 18.3
Acquisition [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Business Combination, Consideration Transferred	$ 57.0
Business Acquisition, Effective Date of Acquisition	Jan. 01, 2017
Acquisition [Member] | Grady and Caddo Counties, Oklahoma [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Area of Land | a	8,300
Proved developed producing wells | wells	47
Acquisition [Member] | McClain County, Oklahoma [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Business combination consideration non-monetary | a	180