a good job/thing...

good job

An informal expression of praise for having done something well. (It can also be used sarcastically to mean the opposite.) Mary: "Dad, I got an A+ on my midterm exam!" Bill: "Good job, sweetie!" Good job, Frank, now we're going to have to rebuild this entire model from scratch.
See also: good, job

(it’s) a good job/thing (that)...

(spoken) (it’s) lucky: It’s a good job he was here. We couldn’t have moved the piano without him.It’s a good job my luggage was insured.
See also: good, job