Commitments and Contingencies (Narrative) (Details) $ in Millions	1 Months Ended		5 Months Ended	9 Months Ended	12 Months Ended
	Apr. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 03, 2014 USD ($)	Mar. 31, 2015 USD ($) lawsuit plaintiff	Jun. 30, 2015 USD ($) $ / item	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Dec. 31, 2014 USD ($)	Sep. 30, 2014 USD ($) agreement $ / item	Dec. 31, 2008 USD ($)	Dec. 31, 2007 USD ($)
Loss Contingencies [Line Items]
Number of class actions lawsuits | lawsuit				3
Number of plantiffs | plaintiff				3
Operating lease expense		$ 1.7	$ 3.0			$ 7.5	$ 2.4
Number of Leases bid upon | agreement									4
Performance bonds					$ 180.8
Required supplemental bonding required by Bureau of Ocean Energy Management					566.5
Supplemental bonds provided to BOEM					54.7
Restricted escrow funds' trust					6.0						$ 15.0
Restricted escrow trust funds including accumulated interest										$ 16.7
Escrow deposit				$ 6.0				$ 6.0	$ 6.0
Subsequent Event [Member]
Loss Contingencies [Line Items]
Supplemental bonds provided to BOEM	$ 566.5
Predecessor Third Party Assignors Including Certain State Regulatory Bodies [Member]
Loss Contingencies [Line Items]
Performance bonds					122.5
Lease Bonds [Member]
Loss Contingencies [Line Items]
Performance bonds					$ 58.3
Through August 11, 2015 [Member]
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item					37,000
Through August 14, 2015 [Member]
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item					70,000
April 1, 2014 to October 12, 2014 [Member]
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item									112,000
July 1, 2014 to October 21, 2014 [Member]
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item									107,500
October 1, 2014 to December 29, 2014
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item									111,380
October 4, 2014 to November 4, 2014 [Member]
Loss Contingencies [Line Items]
Drilling rig commitment per day | $ / item									107,500