Commitments and Contingencies (Details) (Drilling Commitments, USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Drilling Commitments
Construction, Drilling and Purchase Commitments
Commitments for purchases and other expenditures	$ 173.6

The minimum amount the entity agreed to spend under the long-term purchase commitment.

No definition available.

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration