That's not quite right, the NSA is a DoD agency and the highest ranking civilian in it is the Deputy Director. The Director of the NSA is a military officer also in charge of USCYBERCOM.

The FBI and the CIA are indeed civilian agencies (though the CIA has some caveats there).

It might be semantics but NSA being a national defence organization, under the same parent umbrella which forks to Army/Navy/Airforce/Marines, I believe it's fair to lump them in with the 'military':

https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/Do...

The NSA play(ed) a very large role in modern military deployments overseas, especially in the middle east and africa with their targeting systems.

The best counterpoint is the bill Obama passed before leaving office, expanding the data sharing between agencies and the more general significant expansion of scope of the NSAs activities in recent years to involve plenty of domestic and civilian issues (beyond politics) including supporting the efforts on the War on Drugs, DHS, and FBI activities.

Correct on the FBI and CIA; NSA, though is a DoD agency headed by a general and conjoined at the head with both the military Cyber Command and the military Central Security Service.

Continuing the pedantry, DirNSA is currently an admiral (Rogers, specifically).