Long-Lived Asset Impairment (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Long-lived asset impairment
Long-lived asset impairment	$ 3,484	$ 2,486
Idle compressor units
Long-lived asset impairment
Number of long-lived assets that the entity determined to retire and either sell or re-utilize key components	30	25
Horsepower of long-lived assets that the entity determined to sell or re-utilize key components	11,000	7,000
Long-lived asset impairment	$ 3,500	$ 2,500