These are cash-balancing accounts with permanent Funding Option settings—unlimited maximums, fixed surpluses, and deficit orders (the accounts are first and last in each area), and subaccounting is disabled.
Excess Marketable Securities (v2015.00) accumulates cash surpluses, and can be used as a funding source.
Long-Term Debt: Excess (v2690.00) acts as an unlimited long-term revolving facility funding cash deficits not covered by other debt facilities.