Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Trade accounts receivable, allowances for doubtful accounts	$ 1,681	$ 1,496
Patents, trademarks, and other intangible assets, accumulated amortization	$ 12,181	$ 4,771
Partners' capital:
Common units issued and outstanding	33,185,742	33,142,114