Subsequent Events (Details)		3 Months Ended	12 Months Ended
	Feb. 17, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($)	Jan. 05, 2017 right $ / shares shares
Subsequent Event [Line Items]
Common stock, par value | $ / shares			$ 1.00	$ 1.00
Proceeds from sale of oil and gas property and equipment			$ 80,374,000	$ 17,800,000	$ 17,660,000
Non-cash impairment charges			$ 60,939,000	$ 108,184,000	$ 15,934,000
Forecast | The Mineral Companies | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Subsequent Event [Line Items]
Gain on disposition of oil and gas property		$ 82,400,000
Gain of sale of assets		10,600,000
Non-cash impairment charges		$ 37,900,000
Subsequent Event
Subsequent Event [Line Items]
Number of rights issued | right						1
Common stock, par value | $ / shares						$ 1.00
Subsequent Event | The Mineral Companies | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Subsequent Event [Line Items]
Purchase price of properties sold	$ 85,600,000
Proceeds from sale of oil and gas property and equipment	$ 75,000,000
Subsequent Event | Series B Preferred Stock
Subsequent Event [Line Items]
Number of securities called by each right | shares						0.001
Preferred stock, par value | $ / shares						$ 0.01
Purchase price of stock called by each right (dollars in share) | $ / shares						$ 50