Commitments and Contingencies (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Commitments and Contingencies
Purchase orders outstanding for drilling equipment	$ 327.2us-gaap_PurchaseObligation
Gain contingencies recognized in consolidated financial statements	$ 0

Amount of gain recognized in the period that had been disclosed in prior periods as a contingent gain.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 450

-SubTopic 30

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

Name:	us-gaap_FormerGainContingencyRecognizedInCurrentPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant