Dispositions and Acquisitions - Acquisitions - Additional Information (Detail) $ in Thousands, shares in Millions		4 Months Ended	12 Months Ended
	Sep. 16, 2016 USD ($) shares	Dec. 31, 2016 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Merger-related expenses			$ 0	$ 0	$ 37,225
MRD
Business Acquisition [Line Items]
Business merger date			Sep. 16, 2016
Common stock issued in connection with exchange of outstanding shares | shares	77.0
Exchange ratio of common shares for acquired company	0.375
Merger-related expenses	$ 37,200
Revenues		$ 146,600		477,400
Net operating income		$ 94,900		$ 278,800