Summary Box: Banks hit 5-year high in earnings

VERY PROFITABLE YEAR: Last year U.S. banks had their most profitable run since 2006. The surge came largely because banks suffered fewer losses — not from taking in more money.

BIG BANKS DID WELL: The Federal Deposit Insurance Corp. said banks with assets exceeding $10 billion accounted for most of the rise — a 40 percent increase from 2010, to reach $119.5 billion.

SHRINKING LOSS RESERVES: Banks, especially the biggest ones, set aside huge reserves to offset potential losses on loans in the aftermath of the financial crisis. When the losses moderated, banks could log large profits by releasing reserves.