Acquisitions and Dispositions - Acquisitions - Additional Information (Detail) - MRD $ in Thousands		3 Months Ended	6 Months Ended
	Sep. 16, 2016 USD ($) shares	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Business merger date		Sep. 16, 2016
Common stock issued in connection with exchange of outstanding shares | shares	77,042,749
Exchange ratio of common shares for acquired company	0.375
Fair value of outstanding debt	$ 1,204,449
Merger-related expenses			$ 37,200
Revenues		$ 129,100
Net operating income		$ 83,400