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Fund Investment Overview - Additional Information (Detail) (USD $)
 12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Schedule Of Investment [Abstract]    
Deposit with Commodity Broker $ 4,948,283,169us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers $ 6,799,938,046us-gaap_GoodFaithAndMarginDepositsWithBrokerDealers
Percentage of assets held by broker 100.00%dbc_PercentageOfAssetsHeldByBroker 100.00%dbc_PercentageOfAssetsHeldByBroker
Cash and United States Treasury Obligations deposited as margin in support of the Fund's long futures positions $ 272,407,319us-gaap_RestrictedInvestments $ 297,808,276us-gaap_RestrictedInvestments
Percentage of cash and United States Treasury Obligations deposited as margin in support of the Fund's long futures positions 5.51%dbc_PercentageOfHoldingsConsideredRestricted 4.38%dbc_PercentageOfHoldingsConsideredRestricted