insouciant attitude

When a person is incredibly nonchalant about everything in life and just doesn't care about most things or anything they probably are supposed to. Though the word can be used positively or negatively, it basically relates to "not caring much."
It can really annoying coming from an adult you expect to be responsible.

Person 1: Hey, did you complete your part of the presentation on time? The meeting is in two days.
Person 2: Nah... It's whatever... doesn't really matter
Person 1: ...Shouldn't you at least try before it's too late? We're gonna need it
Person 2: Honestly, IDC at this point. I can't stand this job anyway...

Person 3: Wow. He's got such a bad insouciant attitude