How to get confidence interval around ICC from lmer model

I estimate the interrater reliability using ICC from a random-intercept mixed-effects linear regression model. But how to get the confidence interval around the ICC.

elmer <- lmer(A_total ~ (1|Subject), data = data)
summary(elmer)



Linear mixed model fit by REML ['lmerMod']
 Formula: A_total ~ 1 + (1 | Subject)
   Data: data_A

REML criterion at convergence: 184.7

Scaled residuals: 
     Min       1Q   Median       3Q      Max 
-1.41507 -0.29387  0.02918  0.45656  1.27346 

 Random effects:
  Groups   Name        Variance Std.Dev.
  Subject (Intercept) 3663.0   60.52   
  Residual              116.3   10.79   
  Number of obs: 20, groups:  Kodnamn, 10

 Fixed effects:
             Estimate Std. Error t value
 (Intercept)   337.35      19.29   17.49

I calculate ICC to be 3663.0 / (3663.0 + 116.3). But, how can I get the confidence interval around this ICC?