Supplemental Schedule of Cash Flow Information - Non-cash Financing and Investing Activity (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Supplemental Cash Flow Elements [Abstract]
Capital leases and notes issued for equipment	$ 22,374	$ 1,390
Asset retirement obligation additions (retirements)	$ 0	$ 9

Amount of increase (decrease) in asset retirement obligations.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 410
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6392692&loc=d3e7535-110849

Name:	us-gaap_AssetRetirementObligationPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration