Share Purchases and Redemptions - Additional Information (Detail) - 6 months ended Jun. 30, 2015	Basket shares
Equity [Abstract]
Minimum number of Baskets that can be purchased	1
Minimum number of Baskets that can be redeemed	1
Shares Redeemed \| shares	200,000

Minimum Number Of Baskets Of Shares That Can Be Purchased

No definition available.

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Namespace Prefix:	dbb_
Data Type:	xbrli:positiveIntegerItemType
Balance Type:	na
Period Type:	duration