Discontinued Operations (Tables)
 12 Months Ended
Dec. 31, 2014
Discontinued Operations and Disposal Groups [Abstract]  
Schedule of Disposal Groups, Including Discontinued Operations, Income Statement, Balance Sheet and Additional Disclosures [Table Text Block]
The following table presents the revenue, expense and (loss) gain from operations of disposal groups associated with the assets classified as held for sale for the years ended December 31, 2014, 2013, and 2012 (in thousands, except per unit amounts):

 
Year Ended December 31,
 
2014
 
2013
 
2012
Revenue
$
474

 
$
2,084

 
$
2,318

Expense
(658
)
 
(2,361
)
 
(2,336
)
Impairment
(673
)
 
(2,400
)
 
—

Loss on sale of assets
(87
)
 
(75
)
 
—

Income tax benefit
333

 
339

 
—

Gain (loss) from operations of disposal groups, net of tax
$
(611
)
 
$
(2,413
)
 
$
(18
)
Limited partners' net income (loss) per unit from discontinued operations (basic and diluted)
$
(0.04
)
 
$
(0.27
)
 
$
—