Acquisitions and Divestitures - Supplemental Pro Forma Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Revenues		$ 666,508
Net income (loss)		$ 153,843
Basic and diluted earnings per unit		$ 2.20
2015 Beta Acquisition [Member]
Business Acquisition [Line Items]
Revenues	$ 381,495	$ 613,563
Net income (loss)	$ (394,756)	$ 132,630
Basic and diluted earnings per unit	$ (4.73)	$ 1.87