v2.4.1.9

Capital Structure (Details) (USD $)	12 Months Ended			3 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2015	Dec. 31, 2011
Class of Stock [Line Items]
Shares issued under Calpine Equity Incentive Plans	2,566,799us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation	3,022,128us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation	1,741,909us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation
Share repurchase program	(49,684,523)us-gaap_TreasuryStockSharesAcquired	(31,032,110)us-gaap_TreasuryStockSharesAcquired	26,436,677us-gaap_TreasuryStockSharesAcquired
Total common shares outstanding, ending balance	(381,921,264)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve	(429,038,988)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve	(457,048,970)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve		(481,743,738)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve
Common Stock, authorized shares (in shares)	(1,400,000,000)us-gaap_CommonStockSharesAuthorized	(1,400,000,000)us-gaap_CommonStockSharesAuthorized
Common Stock, issued shares (in shares)	(502,287,022)us-gaap_CommonStockSharesIssued	(497,841,056)us-gaap_CommonStockSharesIssued
Common Stock, par value (in dollars per share)	$ (0.001)us-gaap_CommonStockParOrStatedValuePerShare	$ (0.001)us-gaap_CommonStockParOrStatedValuePerShare
Common Stock, outstanding shares (in shares)	(381,921,264)us-gaap_CommonStockSharesOutstanding	(429,038,988)us-gaap_CommonStockSharesOutstanding
Treasury Stock, Shares (in shares)	120,365,758us-gaap_TreasuryStockShares	68,802,068us-gaap_TreasuryStockShares
Treasury Stock, Value	$ 2,345,000,000us-gaap_TreasuryStockValue	$ 1,230,000,000us-gaap_TreasuryStockValue
Treasury Stock, Value, Acquired, Cost Method	(1,115,000,000)us-gaap_TreasuryStockValueAcquiredCostMethod	(636,000,000)us-gaap_TreasuryStockValueAcquiredCostMethod	(469,000,000)us-gaap_TreasuryStockValueAcquiredCostMethod
Shareholder Transaction
Shareholder Ownership Percentage	10.00%cpn_ShareholderOwnershipPercentage
Common Stock Purchased from Shareholder	13,213,372cpn_CommonStockPurchasedfromShareholder
Purchase Price of Common Stock Purchased from Shareholder	311,464,283cpn_PurchasePriceofCommonStockPurchasedfromShareholder
Shares Issued [Member]
Class of Stock [Line Items]
Shares issued under Calpine Equity Incentive Plans	4,445,966us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	5,345,956us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	2,026,285us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember
Share repurchase program	0us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	0us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	0us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember
Total common shares outstanding, ending balance	(502,287,022)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	(497,841,056)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember	(492,495,100)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember		(490,468,815)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_CommonStockMember
Treasury Stock [Member]
Class of Stock [Line Items]
Shares issued under Calpine Equity Incentive Plans	1,879,167us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	2,323,828us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	284,376us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember
Share repurchase program	(49,684,523)us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	(31,032,110)us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	26,436,677us-gaap_TreasuryStockSharesAcquired / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember
Total common shares outstanding, ending balance	(120,365,758)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	(68,802,068)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember	(35,446,130)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember		(8,725,077)cpn_TotalCommonSharesOutstandingIncludingSharesHeldInReserve / us-gaap_StatementClassOfStockAxis = us-gaap_TreasuryStockMember
Share Repurchases in 2014 [Member]
Class of Stock [Line Items]
Share repurchase program	(36,471,151)us-gaap_TreasuryStockSharesAcquired / us-gaap_ShareRepurchaseProgramAxis = cpn_ShareRepurchasesin2014Member
Treasury Stock, Value, Acquired, Cost Method	(789,000,000)us-gaap_TreasuryStockValueAcquiredCostMethod / us-gaap_ShareRepurchaseProgramAxis = cpn_ShareRepurchasesin2014Member
Treasury Stock Acquired, Average Cost Per Share	$ 21.62us-gaap_TreasuryStockAcquiredAverageCostPerShare / us-gaap_ShareRepurchaseProgramAxis = cpn_ShareRepurchasesin2014Member
Subsequent Event [Member] | 2014 Through Filing Date [Member]
Class of Stock [Line Items]
Share repurchase program				(5,772,440)us-gaap_TreasuryStockSharesAcquired / us-gaap_ShareRepurchaseProgramAxis = cpn_A2015ThroughFilingDateMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Treasury Stock, Value, Acquired, Cost Method				$ (125,000,000)us-gaap_TreasuryStockValueAcquiredCostMethod / us-gaap_ShareRepurchaseProgramAxis = cpn_A2015ThroughFilingDateMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Treasury Stock Acquired, Average Cost Per Share				$ 21.68us-gaap_TreasuryStockAcquiredAverageCostPerShare / us-gaap_ShareRepurchaseProgramAxis = cpn_A2015ThroughFilingDateMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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Total Common Shares Outstanding Including Shares Held in Reserve

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Face amount or stated value per share of common stock.

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