Department of Homeland Security 'U.S. Customs and Border Protection' Budget Overview (Fiscal Year 2018 Congressional Justification) [open pdf - 8MB]
From the Component Overview: "U.S. Customs and Border Protection (CBP) is comprised of [various] mission-oriented programs that support achievement of the DHS strategic missions, goals, and objectives. Some programs are indented to show that this is the Procurement, Construction, and Improvements program that supports the related programs. In addition, some fees and funds are indented below the program it most closely aligns to as a funding source."
U.S. Department of Homeland Security: https://www.dhs.gov/