Derivative Financial Instruments Credit Facility and Derivative Counterparties (Details)	Dec. 31, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing	75.00%

Percentage of Proved Oil and Gas Properties Secured for Credit Facility Borrowing

No definition available.

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Namespace Prefix:	sm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant