Bank Holding Companies

They own banks.

Total debt owed (blue; left) and owned (right; red) by bank holding companies.

From wikipedia:

Becoming a bank holding company makes it easier for the firm to raise capital than as a traditional bank. The holding company can assume debt of shareholders on a tax free basis, borrow money, acquire other banks and non-bank entities more easily, and issue stock with greater regulatory ease. It also has a greater legal authority to conduct share repurchases of its own stock. 

The downside includes responding to additional regulatory authorities, especially if there are more than 300 shareholders, at which point the bank holding company is forced to register with the Securities and Exchange Commission. There are also added expenses of operating with an extra layer of administration.

And from Morgan Stanley:

The Firm's status as a Federal Bank Holding Company also provides Morgan Stanley ongoing access to the Federal Reserve Bank Discount Window and expanded opportunities for funding.