Debt (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Debt
Interest Expense	$ 15,397us-gaap_InterestCostsIncurred	$ 10,996us-gaap_InterestCostsIncurred
Amortization-deferred financing costs	2,610us-gaap_AmortizationOfFinancingCosts	2,786us-gaap_AmortizationOfFinancingCosts
Loss on extinguishment of debt		2,898
Capitalized interest	(8,840)us-gaap_InterestCostsCapitalized	(3,801)us-gaap_InterestCostsCapitalized
Deferred interest	1,154kos_DeferredInterest	(4,111)kos_DeferredInterest
Interest income	(168)us-gaap_OtherNonoperatingIncome	(58)us-gaap_OtherNonoperatingIncome
Other, net	598us-gaap_InterestExpenseOther	427us-gaap_InterestExpenseOther
Interest and other financing costs, net	$ 10,751kos_InterestExpenseIncomeNet	$ 9,137kos_InterestExpenseIncomeNet

Amount of deferred interest during the period.

No definition available.

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- Definition

Interest costs charged to earnings during the period, including amortization of deferred financing costs, net gain (loss) on interest rate swap derivatives, loss of extinguishment of debt, and net of interest income.

+ References

No definition available.

+ Details

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- Definition

Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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- Definition

Amount of interest capitalized during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Allowance for Funds Used during Construction

-URI http://asc.fasb.org/extlink&oid=6504829

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- Definition

Total interest costs incurred during the period and either capitalized or charged against earnings.

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- Definition

Interest expense on all other items not previously classified. For example, includes dividends associated with redeemable preferred stock of a subsidiary that is treated as a liability in the parent's consolidated balance sheet.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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- Definition

The aggregate amount of other income amounts, the components of which are not separately disclosed on the income statement, resulting from ancillary business-related activities (that is, excluding major activities considered part of the normal operations of the business) also known as other nonoperating income recognized for the period. Such amounts may include: (a) dividends, (b) interest on securities, (c) profits on securities (net of losses), and (d) miscellaneous other income items.

+ References

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