This series is a sum of total reserve balances maintained plus vault cash used to satisfy required reserves.
Effective February 2, 1984, reserve computation and maintenance periods have been changed from weekly to bi-weekly. Series with data prior to February 2, 1984 have different values reported from one week to the next. After February 2, 1984, the value repeats for 2 consecutive weeks.
Board of Governors of the Federal Reserve System (US), Reserves of Depository Institutions, Total [TOTRESNSW], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/TOTRESNSW, March 22, 2018.