Fair Value Measurements (Narrative) (Details) $ in Thousands, lb in Millions	6 Months Ended
	Jun. 30, 2017 USD ($) property lb $ / lb	Jun. 30, 2016 USD ($) property	Dec. 31, 2016 USD ($)
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Number of years long-term sales growth forecasted over	6 years
Average long-term sales growth forecast, over next 4 years, percent per year	14.00%
Combined carrying value	$ 203,204	$ 151,250	$ 172,748
Derivative, Nonmonetary Notional Amount, Mass | lb	26.4
Underlying, Derivative Mass | $ / lb	0.25
Derivative Asset	$ 1,900
Derivative, Gain (Loss) on Derivative, Net	$ 400
Vacant owned facilities
Fair Value, Balance Sheet Grouping, Financial Statement Captions
Number of vacant owned facilities | property	1	1
Number of properties classified as fixed assets | property	1	1
Estimated combined fair value	$ 3,000	$ 3,000
Combined carrying value	$ 2,500	$ 2,500