Acquisitions - Additional Information (Detail) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
	Apr. 01, 2015 USD ($) mi	Jun. 30, 2016 USD ($) $ / shares shares	Jun. 30, 2015 USD ($) $ / shares	Jun. 30, 2016 USD ($) $ / shares	Jun. 30, 2015 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Transaction costs						$ (514)	$ (786)
Revenues		$ 102,342	$ 92,682	$ 248,638	$ 262,763
Net income		$ 8,029	$ 6,294	$ 28,396	$ 27,403	41,140
Diluted (in dollars per share) | $ / shares		$ 0.52	$ 0.41	$ 1.85	$ 1.83
Goodwill		$ 15,070		$ 15,070		14,548
Gatherco [Member]
Business Acquisition [Line Items]
Number of pipeline miles | mi	2,500
Number of counties served	40
Number of producers served	300
Number of customers served	20,000
Purchase price		$ 57,658
Shares of common stock issued at closing (shares) | shares		592,970
Common stock issued at closing	$ 30,200	$ 30,164		30,164
Cash paid	27,500	27,494
Long-term debt	1,696	1,696		1,696
Cash acquired	6,800	6,806		6,806
Additional contingent cash consideration		$ 15,000		15,000
Period for revenue generated from potential new gathering opportunities		5 years
Transaction costs						$ (1,300)
Revenues		$ 4,800		12,800
Net income		$ 28		1,700
Diluted (in dollars per share) | $ / shares		$ 0.03
Goodwill	$ 11,100	$ 10,119		$ 10,119