CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
CONSOLIDATED STATEMENTS OF CASH FLOWS
Cash settlements on derivatives (including $225.5 million, $18.4 million and $(22.3) million on commodity hedges)	$ 225.5	$ 18.4	$ (22.3)

Represents the amount of cash settlements on commodity derivatives

No definition available.

Name:	kos_CashSettlementsOnCommodityDerivatives
Namespace Prefix:	kos_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration