Capitalized Exploratory Well Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($)
Capitalized Exploratory Well Costs [Abstract]
Capitalized exploratory well costs, beginning balance	$ 2.6
Capitalized exploratory well costs, ending balance	14.1
Additions to capitalized exploratory well costs pending the determination of proved reserves	$ 11.5