Acquisitions - Unaudited Pro Forma Financial Information (Detail) - BRMR and Everest Merger Sub Inc. [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Pro forma total revenues	$ 155,539	$ 140,936	$ 339,694	$ 274,836
Pro forma net income (loss)	$ 27,505	$ (30,544)	$ (230)	$ (40,287)
Pro forma net income (loss) per share (basic and diluted)	$ 0.77	$ (0.86)	$ (0.01)	$ (1.14)