Organization - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2020 CreationUnit shares	Dec. 31, 2019 shares	Aug. 03, 2006 Trust shares
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of series of trusts | Trust			7
General shares, shares issued	40	40	40
Treasury obligation measurement maximum maturity period	12 months
Minimum number of Creation Units that can be purchased | CreationUnit	1
Number of shares issued per Creation Unit	200,000