Acquisitions - Additional Information (Detail) $ / shares in Units, $ in Thousands			3 Months Ended		12 Months Ended
	May. 07, 2015 USD ($)	Apr. 01, 2015 USD ($) mi	Mar. 31, 2016 USD ($) $ / shares shares	Mar. 31, 2015 USD ($) $ / shares	Dec. 31, 2015 USD ($)
Business Acquisition [Line Items]
Transaction costs					$ (514)
Revenues			$ 146,296	$ 170,081
Net income			$ 20,367	$ 21,109	41,140
Diluted (in dollars per share) | $ / shares			$ 1.33	$ 1.44
Goodwill			$ 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
Cash paid		27,500	27,494
Long-term debt		1,696	1,696
Cash acquired		6,800	6,806
Additional contingent cash consideration			$ 15,000
Period for revenue generated from potential new gathering opportunities			5 years
Transaction costs					$ (1,300)
Revenues			$ 7,900
Net income			$ 1,676
Diluted (in dollars per share) | $ / shares			$ 0.03
Goodwill		$ 11,100	$ 10,119
Propane Distribution [Member]
Business Acquisition [Line Items]
Number of customers served	253
Purchase price	$ 242
Intangible assets	$ 186
Minimum [Member] | Propane Distribution [Member]
Business Acquisition [Line Items]
Amortization period			6 years
Maximum [Member] | Propane Distribution [Member]
Business Acquisition [Line Items]
Amortization period			10 years