 JPMorgan set aside $3.1 billion to cover potentially bad loans. That's up sharply from a year ago, as the bank acknowledged that delinquencies were climbing among some Americans. Meanwhile, Citigroup had to set aside more for potential losses as well. But there's a but here. At the same time, JPMorgan Chase, the nation's biggest bank by assets, on Friday posted a profit of $18.1 billion.