Stockholders' Equity - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017 USD ($) shares	Sep. 30, 2016 USD ($)	Jun. 30, 2017 shares	Mar. 31, 2017 shares	Jan. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares
Class of Stock [Line Items]
Proceeds from the issuance of common stock | $	$ 218,195,000	$ 58,886,000
Shares issued value | $	$ 217,088,000	$ 57,374,000
Common stock, shares issued | shares	214,000,000					109,600,000
Shares issued value | $	$ 1,943,000					$ 101,000
Conversion ratio	1
At-the-Market Program
Class of Stock [Line Items]
Number of shares issued | shares	1,000,000.0
Shares issued value | $	$ 10,300,000
Fees and commissions | $	500,000
Maximum | At-the-Market Program
Class of Stock [Line Items]
Proceeds from the issuance of common stock | $	$ 200,000,000
TOTAL Delaware Inc
Class of Stock [Line Items]
Common stock, shares issued | shares					35,400,000
Shares issued value | $					$ 207,000,000
Shares exchanged for issue of common stock | shares					46,000,000
GE Oil & Gas, Inc.
Class of Stock [Line Items]
Number of shares converted | shares			5,500,000
GE Oil & Gas, Inc. | Series A Preferred Stock
Class of Stock [Line Items]
Number of shares converted | shares				5,500,000
GE Oil & Gas, Inc. | Series B Preferred Stock
Class of Stock [Line Items]
Number of shares converted | shares			5,500,000