Long-Term Incentive Plan and Unit Appreciation Right Activity (Detail) - shares		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Restricted phantom units | 2014 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period		105,167	4,241	102,661	2,189
Granted	[1]	4,923	2,040	7,429	4,092
Outstanding, end of period	[2]	110,090	6,281	110,090	6,281
Restricted phantom units | 2004 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period		188,948	172,793	184,457	169,122
Granted	[3]	5,137	3,556	9,628	7,227
Outstanding, end of period	[4]	194,085	176,349	194,085	176,349
Unit appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, beginning of period		66,793	112,346	66,793	123,000
Outstanding, end of period	[5]	66,793	87,021	66,793	87,021
Exercised			(19,595)		(30,249)
Forfeited			(5,730)		(5,730)
Exercisable, end of period		44,968	41,383	44,968	41,383

[1] The weighted-average grant date fair value for the unit awards on the date of grant was $23.95 and $29.52 for three months ended June 30, 2016 and 2015, respectively, and $24.60 and $29.11 for six months ended June 30, 2016 and 2015, respectively. The intrinsic value of vested unit awards was $0.1 million for both the three months ended June 30, 2016 and 2015 and $0.2 million and $0.1 million for the six months ended June 30, 2016 and 2015, respectively.

[2] Based on the closing price of the common units on June 30, 2016, the estimated intrinsic value of the outstanding unit awards was $2.8 million at June 30, 2016.

[3] The weighted-average fair value for the phantom units credited was $23.52 and $30.04 for the three months ended June 30, 2016 and 2015, respectively, and $24.80 and $29.02 for the six months ended June 30, 2016 and 2015, respectively. The intrinsic value of vested phantom unit awards was $0.1 million for both the three months ended June 30, 2016 and 2015 and $0.2 million for both the six months ended June 30, 2016 and 2015.

[4] Based on the closing price of the common units on June 30, 2016, the estimated intrinsic value of the outstanding unit awards was $4.9 million at June 30, 2016.

[5] Based on the closing price of the common units on June 30, 2016, the estimated intrinsic value of the outstanding unit awards was $0.1 million at June 30, 2016. The weighted average remaining contractual life for outstanding UAR awards at June 30, 2016 was 2.1 years.