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Property, Plant and Equipment - Capitalized Costs of Unproved Properties Excluded from Amortization (Additional Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Abstract]
Pipe inventory costs, cumulative	$ 34.7
Pipe inventory costs, period costs	$ 10.5	$ 6.2	$ 18.0