1.0.0.3 true CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY AND COMPREHENSIVE INCOME (LOSS) (USD $) In Thousands false 1 $ true false false false Common Stock us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_CommonStockMember us-gaap_StatementEquityComponentsAxis explicitMember Shares Standard http://www.xbrl.org/2003/instance shares xbrli 0 USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 2 $ true false false false Paid-in Capital us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_AdditionalPaidInCapitalMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 3 $ true false false false Retained Earnings us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_RetainedEarningsMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 4 $ true false false false Accumulated Other Comprehensive Income (loss) us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_AccumulatedOtherComprehensiveIncomeMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 5 $ true false false false Treasury Stock us-gaap_StatementEquityComponentsAxis xbrldi http://xbrl.org/2006/xbrldi us-gaap_TreasuryStockMember us-gaap_StatementEquityComponentsAxis explicitMember USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 false 6 $ false false USD Standard http://www.xbrl.org/2003/iso4217 USD iso4217 0 USDPerShare Divide http://www.xbrl.org/2003/iso4217 USD iso4217 http://www.xbrl.org/2003/instance shares xbrli 0 6 Balance at Dec. 31, 2006 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false true false false true false false 1 true true 840000 840 true false 2 true true 1886457000 1886457 true false 3 true true 1115442000 1115442 true false 4 true true 31081000 31081 true false 5 true true -40628000 -40628 true false 6 true true 2993192000 2993192 false false No definition available. No authoritative reference available. false 7 Balance, shares at Dec. 31, 2006 4 us-gaap_SharesIssued us-gaap true na instant shares No definition available. false false false true false false true false false 1 false true 83962000 83962 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 5 Increase (Decrease) in Stockholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 8 Dividends 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true -15109000 -15109 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -15109000 -15109 false false No definition available. No authoritative reference available. false 9 Issuance of restricted stock awards 4 us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 5000 5 true false 2 false true -5000 -5 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 10 Issuance of restricted stock awards, shares 5 us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 572000 572 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 11 Treasury Stock 4 us-gaap_TreasuryStockValueAcquiredCostMethod us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false true -42266000 -42266 true false 6 false true -42266000 -42266 false false No definition available. No authoritative reference available. false 14 Common stock reacquired and retired 4 us-gaap_StockRepurchasedAndRetiredDuringPeriodValue us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -13000 -13 true false 2 false true -49270000 -49270 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false true 42266000 42266 true false 6 false true -7017000 -7017 false false No definition available. No authoritative reference available. false 15 Common stock reacquired and retired, shares 5 us-gaap_StockRepurchasedAndRetiredDuringPeriodShares us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true -1306000 -1306 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 16 Restricted stock forfeited and retired 4 xec_StockIssuedDuringPeriodValueRestrictedStockAwardForfeitedAndRetired xec false debit duration monetary Value of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -1000 -1 true false 2 false true 1000 1 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Value of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 17 Restricted stock forfeited and retired, shares 5 xec_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeitedAndRetired xec false na duration shares Number of shares of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -61000 -61 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Number of shares of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 18 Amortization of unearned compensation 4 xec_AdjustmentsToAdditionalPaidInCapitalAndUnearnedCompensationAmortizationOfUnearnedCompensation xec false credit duration monetary Represents the amortization of unearned compensation recognized during the period arising from share-based compensation... false false false false false false false false false 1 false false 0 0 true false 2 false true 12738000 12738 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 12738000 12738 false false Represents the amortization of unearned compensation recognized during the period arising from share-based compensation arrangements (for example, shares of stock or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. No authoritative reference available. false 19 Exercise of stock options, net of tax benefit of $4,026 for 2007, $6,712 for 2008, and $1,208 for 2009 recorded in paid-in capital 4 xec_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTax xec false credit duration monetary Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in... false false false false false false false false false 1 false true 5000 5 true false 2 false true 9881000 9881 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 9886000 9886 false false Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in capital. No authoritative reference available. false 20 Exercise of stock options, shares 5 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 454000 454 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 21 Stock Option Compensation Expense 4 us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false true 1897000 1897 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 1897000 1897 false false No definition available. No authoritative reference available. false 24 Comprehensive income (loss): 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 25 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true 345262000 345262 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 345262000 345262 false false No definition available. No authoritative reference available. false 26 Net change from hedging activity 5 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false true -23302000 -23302 true false 5 false false 0 0 true false 6 false true -23302000 -23302 false false No definition available. No authoritative reference available. false 27 Unrealized change in short-term investments and other, net of tax 5 xec_OtherComprehensiveIncomeUnrealizedGainLossOnShortTermInvestmentsAndOtherNetOfTax xec false credit duration monetary Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other,... false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false true -153000 -153 true false 5 false false 0 0 true false 6 false true -153000 -153 false false Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other, net of tax. No authoritative reference available. false 28 Total comprehensive income (loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 321807000 321807 false false No definition available. No authoritative reference available. true 29 Balance at Dec. 31, 2007 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false true false false false true false 1 false true 836000 836 true false 2 false true 1861699000 1861699 true false 3 false true 1445595000 1445595 true false 4 false true 7626000 7626 true false 5 false true -40628000 -40628 true false 6 false true 3275128000 3275128 false false No definition available. No authoritative reference available. false 30 Balance, shares at Dec. 31, 2007 4 us-gaap_SharesIssued us-gaap true na instant shares No definition available. false false false true false false false true false 1 false true 83621000 83621 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 5 Increase (Decrease) in Stockholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 8 Dividends 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true -20079000 -20079 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -20079000 -20079 false false No definition available. No authoritative reference available. false 9 Issuance of restricted stock awards 4 us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 5000 5 true false 2 false true -5000 -5 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 10 Issuance of restricted stock awards, shares 5 us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 465000 465 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 12 Retirement of treasury stock 4 us-gaap_TreasuryStockValueRetiredCostMethod us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -2000 -2 true false 2 false true -7282000 -7282 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false true 7284000 7284 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 13 Retirement of treasury stock, shares 5 us-gaap_TreasuryStockSharesRetired us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true -193000 -193 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 14 Common stock reacquired and retired 4 us-gaap_StockRepurchasedAndRetiredDuringPeriodValue us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false true -1000 -1 true false 2 false true -9938000 -9938 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -9939000 -9939 false false No definition available. No authoritative reference available. false 15 Common stock reacquired and retired, shares 5 us-gaap_StockRepurchasedAndRetiredDuringPeriodShares us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true -154000 -154 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 16 Restricted stock forfeited and retired 4 xec_StockIssuedDuringPeriodValueRestrictedStockAwardForfeitedAndRetired xec false debit duration monetary Value of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -1000 -1 true false 2 false true 1000 1 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Value of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 17 Restricted stock forfeited and retired, shares 5 xec_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeitedAndRetired xec false na duration shares Number of shares of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -54000 -54 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Number of shares of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 18 Amortization of unearned compensation 4 xec_AdjustmentsToAdditionalPaidInCapitalAndUnearnedCompensationAmortizationOfUnearnedCompensation xec false credit duration monetary Represents the amortization of unearned compensation recognized during the period arising from share-based compensation... false false false false false false false false false 1 false false 0 0 true false 2 false true 15491000 15491 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 15491000 15491 false false Represents the amortization of unearned compensation recognized during the period arising from share-based compensation arrangements (for example, shares of stock or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. No authoritative reference available. false 19 Exercise of stock options, net of tax benefit of $4,026 for 2007, $6,712 for 2008, and $1,208 for 2009 recorded in paid-in capital 4 xec_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTax xec false credit duration monetary Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in... false false false false false false false false false 1 false true 4000 4 true false 2 false true 13137000 13137 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 13141000 13141 false false Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in capital. No authoritative reference available. false 20 Exercise of stock options, shares 5 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 414000 414 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 21 Stock Option Compensation Expense 4 us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false true 1731000 1731 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 1731000 1731 false false No definition available. No authoritative reference available. false 23 Vesting of restricted stock units, shares 5 xec_StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits xec false na duration shares The number of shares issued during the period related to the vesting of restricted stock units. false false false false false false false false false 1 false true 45000 45 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false The number of shares issued during the period related to the vesting of restricted stock units. No authoritative reference available. false 24 Comprehensive income (loss): 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 25 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true -915245000 -915245 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -915245000 -915245 false false No definition available. No authoritative reference available. false 26 Net change from hedging activity 5 us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPeriodIncreaseDecrease us-gaap true na duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false true -7652000 -7652 true false 5 false false 0 0 true false 6 false true -7652000 -7652 false false No definition available. No authoritative reference available. false 27 Unrealized change in short-term investments and other, net of tax 5 xec_OtherComprehensiveIncomeUnrealizedGainLossOnShortTermInvestmentsAndOtherNetOfTax xec false credit duration monetary Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other,... false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false true -929000 -929 true false 5 false false 0 0 true false 6 false true -929000 -929 false false Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other, net of tax. No authoritative reference available. false 28 Total comprehensive income (loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -923826000 -923826 false false No definition available. No authoritative reference available. true 29 Balance at Dec. 31, 2008 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false true false false false true false 1 false true 841000 841 true false 2 false true 1874834000 1874834 true false 3 false true 510271000 510271 true false 4 false true -955000 -955 true false 5 false true -33344000 -33344 true false 6 false true 2351647000 2351647 false false No definition available. No authoritative reference available. false 30 Balance, shares at Dec. 31, 2008 4 us-gaap_SharesIssued us-gaap true na instant shares No definition available. false false false true false false false true false 1 false true 84144000 84144 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 5 Increase (Decrease) in Stockholders' Equity 3 us-gaap_IncreaseDecreaseInStockholdersEquityRollForward us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 8 Dividends 4 us-gaap_DividendsCommonStockCash us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true -20293000 -20293 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -20293000 -20293 false false No definition available. No authoritative reference available. false 9 Issuance of restricted stock awards 4 us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true 4000 4 true false 2 false true -4000 -4 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 10 Issuance of restricted stock awards, shares 5 us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 381000 381 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 12 Retirement of treasury stock 4 us-gaap_TreasuryStockValueRetiredCostMethod us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false true -9000 -9 true false 2 false true -33335000 -33335 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false true 33344000 33344 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 13 Retirement of treasury stock, shares 5 us-gaap_TreasuryStockSharesRetired us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true -885000 -885 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 14 Common stock reacquired and retired 4 us-gaap_StockRepurchasedAndRetiredDuringPeriodValue us-gaap true debit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false true -2440000 -2440 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -2440000 -2440 false false No definition available. No authoritative reference available. false 15 Common stock reacquired and retired, shares 5 us-gaap_StockRepurchasedAndRetiredDuringPeriodShares us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true -78000 -78 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 16 Restricted stock forfeited and retired 4 xec_StockIssuedDuringPeriodValueRestrictedStockAwardForfeitedAndRetired xec false debit duration monetary Value of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -2000 -2 true false 2 false true 2000 2 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Value of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 17 Restricted stock forfeited and retired, shares 5 xec_StockIssuedDuringPeriodSharesRestrictedStockAwardForfeitedAndRetired xec false na duration shares Number of shares of stock related to restricted stock awards forfeited and retired during the period. false false false false false false false false false 1 false true -159000 -159 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false Number of shares of stock related to restricted stock awards forfeited and retired during the period. No authoritative reference available. false 18 Amortization of unearned compensation 4 xec_AdjustmentsToAdditionalPaidInCapitalAndUnearnedCompensationAmortizationOfUnearnedCompensation xec false credit duration monetary Represents the amortization of unearned compensation recognized during the period arising from share-based compensation... false false false false false false false false false 1 false false 0 0 true false 2 false true 13404000 13404 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 13404000 13404 false false Represents the amortization of unearned compensation recognized during the period arising from share-based compensation arrangements (for example, shares of stock or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees. No authoritative reference available. false 19 Exercise of stock options, net of tax benefit of $4,026 for 2007, $6,712 for 2008, and $1,208 for 2009 recorded in paid-in capital 4 xec_StockIssuedDuringPeriodValueStockOptionsExercisedNetOfTax xec false credit duration monetary Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in... false false false false false false false false false 1 false true 1000 1 true false 2 false true 3420000 3420 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 3421000 3421 false false Value of stock issued during the period as a result of the exercise of stock options, net of tax benefit recorded in paid in capital. No authoritative reference available. false 20 Exercise of stock options, shares 5 us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised us-gaap true na duration shares No definition available. false false false false false false false false false 1 false true 134000 134 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false 21 Stock Option Compensation Expense 4 us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false true 3374000 3374 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true 3374000 3374 false false No definition available. No authoritative reference available. false 23 Vesting of restricted stock units, shares 5 xec_StockIssuedDuringPeriodSharesVestingOfRestrictedStockUnits xec false na duration shares The number of shares issued during the period related to the vesting of restricted stock units. false false false false false false false false false 1 false true 5000 5 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false The number of shares issued during the period related to the vesting of restricted stock units. No authoritative reference available. false 24 Comprehensive income (loss): 4 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterestAbstract us-gaap true na duration string No definition available. false false false false false true false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. false 25 Net income (loss) 5 us-gaap_ProfitLoss us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false true -311943000 -311943 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -311943000 -311943 false false No definition available. No authoritative reference available. false 27 Unrealized change in short-term investments and other, net of tax 5 xec_OtherComprehensiveIncomeUnrealizedGainLossOnShortTermInvestmentsAndOtherNetOfTax xec false credit duration monetary Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other,... false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false true 936000 936 true false 5 false false 0 0 true false 6 false true 936000 936 false false Appreciation or loss in value of the total of unsold short-term investments during the period being reported on and other, net of tax. No authoritative reference available. false 28 Total comprehensive income (loss) 5 us-gaap_ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit duration monetary No definition available. false false false false false false false false false 1 false false 0 0 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false true -311007000 -311007 false false No definition available. No authoritative reference available. true 29 Balance at Dec. 31, 2009 4 us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest us-gaap true credit instant monetary No definition available. false false false true false false false true false 1 true true 835000 835 true false 2 true true 1859255000 1859255 true false 3 true true 178035000 178035 true false 4 true true -19000 -19 true false 5 false false 0 0 true false 6 true true 2038106000 2038106 false false No definition available. No authoritative reference available. false 30 Balance, shares at Dec. 31, 2009 4 us-gaap_SharesIssued us-gaap true na instant shares No definition available. false false false true false false false true false 1 false true 83542000 83542 true false 2 false false 0 0 true false 3 false false 0 0 true false 4 false false 0 0 true false 5 false false 0 0 true false 6 false false 0 0 false false No definition available. No authoritative reference available. false false 6 65 false Thousands Thousands UnKnown false true