Use fixed position instead of sticky for sidenav and top bar so it works in IE

styles/components/_global_layout.scss

@@ -25,9 +25,12 @@ body {
     margin: $gap;
     flex-grow: 1;
     -ms-flex-negative: 1;
+    top: 68px;
+    position: relative;
 
     @include media($medium-screen) {
       margin: $gap * 2;
+      top: 68px;
     }
   }
 }

styles/components/_sticky_cta.scss

@@ -9,7 +9,7 @@
   }
 
   &.js-is-sticky {
-    width: 80.8%;
+    width: calc(100% - 25rem);
   }
 
   .sticky-cta-container {

styles/components/_topbar.scss

@@ -2,11 +2,10 @@
   background-color: $color-blue-darkest;
   border-bottom: 1px solid $color-black;
   height: 48px;
-
-  &.js-is-sticky {
-    width: 100%;
-    z-index: 16;
-  }
+  position: fixed;
+  top: 20px;
+  width: 100%;
+  z-index: 10;
 
   &__navigation {
     display: flex;

styles/components/_usa_banner.scss

@@ -3,6 +3,9 @@
   align-items: center;
   padding: ($gap / 2) $gap;
   z-index: 15;
+  position: fixed;
+  height: 20px;
+  width: 100%;
 
   img {
     flex-grow: 0;

styles/elements/_sidenav.scss

@@ -5,17 +5,30 @@
 
 .sidenav-container {
   box-shadow: $box-shadow;
+  overflow: hidden;
+  position: relative;
+  top: 68px;
 
-  .sidenav {
-    @include media($large-screen) {
-      margin: 0px;
-    }
-
+  &__toggler {
     width: 25rem;
 
-    &.js-is-sticky {
-      width: 19.2%;
-      min-width: 25rem;
+    &--minimized {
+      @extend .sidenav-container__toggler;
+      width: 10rem;
+    }
+  }
+
+  &__fixed {
+    position: fixed;
+    overflow: scroll;
+  }
+
+  .sidenav {
+    width: 25rem;
+    overflow: scroll;
+
+    @include media($large-screen) {
+      margin: 0px;
     }
 
     &__title {
@@ -184,9 +197,5 @@
 
     width: 10rem;
     margin: 0px;
-
-    &.js-is-sticky {
-      width: 10rem;
-    }
   }
 }