Acquisitions - Additional Information (Detail) $ in Thousands			3 Months Ended								12 Months Ended
	May. 07, 2015 USD ($)	Apr. 01, 2015 USD ($) mi	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($)	Jun. 30, 2014 USD ($)	Mar. 31, 2014 USD ($)	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed											$ 514
Cash paid for acquisition											20,930	$ 0	$ 20,201
Revenues			$ 104,567	$ 91,913	$ 92,682	$ 170,081	$ 120,380	$ 91,619	$ 100,497	$ 186,337	459,244	498,834	444,306
Net Income			8,619	$ 5,119	$ 6,294	$ 21,109	10,097	$ 3,180	$ 5,134	$ 17,681	41,140	36,092	32,787
Goodwill			14,548				4,952				14,548	4,952
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			30,164				$ 0				$ 30,164	0	0
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life											10 years
Propane Distribution [Member]
Number of Customers Served	253
Business Combination, Consideration Transferred	$ 242
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles	$ 186
Acquired Finite-lived Intangible Assets, Weighted Average Useful Life											6 years
Gatherco [Member]
Business Combination Contingent Cash Consideration Payable			15,000								$ 15,000
Period Additional Contingent Cash Consideration Will Be Based On											5 years
Business Combination, Separately Recognized Transactions, Additional Disclosures, Acquisition Cost Expensed											$ 1,300
Cash paid for acquisition		$ 27,500									27,494
Number of Pipeline Miles | mi		2,500
Number of Counties Served		40
Number of Producers Served		300
Number of Customers Served		20,000
Business Combination, Consideration Transferred											57,658
Revenues											16,700
Net Income											312
Goodwill		$ 11,100	9,596								9,596
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned		30,200	30,164								$ 30,164
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares											592,970
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Liabilities, Long-term Debt		1,696	1,696								$ 1,696
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 6,800	$ 6,806								$ 6,806
BravePoint Group [Member]
Revenues												15,100	19,100
Net Income												$ (232)	$ (155)