CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONSOLIDATED STATEMENTS OF CASH FLOWS
Cash settlements on derivatives, net (including $187.9 million, $225.5 million and $18.4 million on commodity hedges during 2016, 2015 and 2014)	$ 187.9	$ 225.5	$ 18.4

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