Acquisitions - Unaudited Pro Forma Financial Information (Detail) - BRMR and Everest Merger Sub Inc. [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Pro forma total revenues	$ 163,294	$ 176,925	$ 502,989	$ 451,761
Pro forma net income (loss)	$ 8,220	$ 10,127	$ 26,638	$ (30,160)
Pro forma net income (loss) per share (basic and diluted)	$ 0.23	$ 0.28	$ 0.75	$ (0.85)