Derivative Instruments and Hedging Activities - Before Tax Effect of Derivative Instruments in Statement of Operations (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Decrease/increase in oil revenue owing to effective hedging contracts	$ 1.3	$ 7.5	$ 10.0	$ 2.4
Decrease/increase in gas revenue owing to effective hedging contracts		$ 5.4	$ 7.6	$ 11.4

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income (specifically into oil and condensate revenue) on derivative instruments designated and qualifying as hedging instruments.

No definition available.

Name:	sgy_DecreaseIncreaseInOilRevenueOwingToEffectiveHedgingContracts
Namespace Prefix:	sgy_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration