Quarterly Results of Operations (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule Of Quarterly Financial Information [Line Items]
Revenues	$ 63,068	$ 61,539	$ 62,422	$ 59,612	$ 59,314	$ 62,197	$ 61,508	$ 59,587	$ 246,641	$ 242,606	$ 228,388
Net income (loss)	(3,539)	(1,484)	(11,809)	(2,200)	(3,935)	1,061	(2,169)	2,030	(19,032)	(3,013)	(9,715)
General partner's interest in net income (loss) for the period	(66)	(26)	(218)	(40)	(79)	21	(43)	41	(350)	(60)	(194)
Limited partners' interest in net income (loss) for the period	$ (3,473)	$ (1,458)	$ (11,591)	$ (2,160)	$ (3,856)	$ 1,040	$ (2,126)	$ 1,989	$ (18,682)	$ (2,953)	$ (9,521)
Net income (loss) per limited partner unit
Basic and diluted	$ (0.16)	$ (0.07)	$ (0.54)	$ (0.11)
Basic					$ (0.20)	$ 0.05	$ (0.11)	$ 0.10
Diluted					$ (0.20)	$ 0.05	$ (0.11)	$ 0.10