CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
CONDENSED CONSOLIDATED BALANCE SHEETS
Accounts receivable, trade, allowance (in dollars)	$ 1,192	$ 1,253
Common units, units issued	59,789,158	55,724,022
General partner units, interest (as a percent)	2.00%	2.00%
General partner units, equivalent units issued	1,209,562	1,129,221
General partner units, equivalent units outstanding	1,209,562	1,129,221
Treasury units, common units	72,674	61,665