The FRED series Debt Outstanding Domestic Nonfinancial Sectors - Total Business Sector is now known as Nonfinancial Business; Credit Market Instruments; Liability.
The source series id is LA144104005.Q.
This series appears in Table D.3. For further information see the assistance provided in the guide to the Financial Accounts at http://www.federalreserve.gov/apps/fof/.
Board of Governors of the Federal Reserve System (US), Nonfinancial Business; Credit Market Instruments; Liability, Level [TBSDODNS], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/TBSDODNS, March 23, 2018.