KK w/ 3 Aces on board

[moose47]

Alright, I have CO at 18/5/1 through about 60 hands. He is also a 2+2er and a very solid player. No reads on anyone else.

PokerStars 0.02/0.04 Hold'em (8 handed) converter

Preflop: Hero is UTG+1 with K[img]/images/graemlins/heart.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
UTG calls, <font color="#CC3333">Hero raises</font>, MP1 calls, MP2 calls, CO calls, <font color="#666666">3 folds</font>, UTG calls.

Flop: (11.50 SB) Q[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img], A[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(5 players)</font>
UTG checks, <font color="#CC3333">Hero bets</font>, MP1 folds, MP2 folds, CO calls, UTG calls.

Turn: (7.25 BB) A[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(3 players)</font>
UTG checks, <font color="#CC3333">Hero bets</font>, CO calls, UTG folds.

River: (9.25 BB) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">CO raises</font>, Hero calls.

Final Pot: 13.25 BB

I'm almost sure I'm beat when I'm raised on the river but I called anyway hoping to see JJ or QQ. Against a solid player was this overplayed on my part or will he show a high pocket pair enough times to justify staying aggressive?