CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
CONSOLIDATED STATEMENTS OF CASH FLOWS
Cash settlements on derivatives, net (including $11.4 million and $56.6 million on commodity hedges during 2017 and 2016)	$ 11.4	$ 56.6

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