a good job/thing...

good job

informal An 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
Farlex Dictionary of Idioms.

(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
Farlex Partner Idioms Dictionary
See also:
  • do a good job
  • for good measure
  • do (one) a/the world of good
  • do no good
  • be as good as new
  • as good as it gets
  • (one) (has) never had it so good
  • (as) good as new
  • as good as new
  • expecations