diff --git a/core/modules/system/system.theme.css b/core/modules/system/system.theme.css
index 3f336bc..7d6ad8a 100644
--- a/core/modules/system/system.theme.css
+++ b/core/modules/system/system.theme.css
@@ -195,7 +195,7 @@ details {
   margin-bottom: 1em;
 }
 details > .details-wrapper {
-  padding: 0.5em 1.5em;
+  padding: 0.5em 1.25em;
 }
 /* @todo Regression: The summary of uncollapsible details are no longer
      vertically aligned with the .details-wrapper in browsers without native
@@ -207,14 +207,14 @@ summary {
   padding-left: 0.5em;
   padding-right: 0.5em;
 }
-.collapse-processed > summary:before {
+.collapse-processed .details-title:before {
   background: url(../../misc/menu-expanded.png) 0px 100% no-repeat; /* LTR */
   content: "";
   float: left;
   height: 1em;
   width: 1em;
 }
-.collapse-processed:not([open]) > summary:before {
+.collapse-processed:not([open]) .details-title:before {
   background-position: 25% 35%; /* LTR */
   -moz-transform: rotate(-90deg);
   -ms-transform: rotate(-90deg);
diff --git a/core/themes/seven/style.css b/core/themes/seven/style.css
index b68ac56..f701ab6 100644
--- a/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -503,8 +503,7 @@ details {
   line-height: 1.295em;
 }
 details summary {
-  padding-top: 0.5em;
-  padding-bottom: 0.5em;
+  padding: 0.75em 1.25em;
 }
 details details {
   background-color: #fff;
@@ -512,6 +511,20 @@ details details {
 details details details {
   background-color: #f8f8f8;
 }
+.collapsible summary {
+  color: #0074bd; /* link color */
+  cursor: pointer;
+}
+.collapsible summary:hover {
+  text-decoration: underline;
+}
+.collapse-processed summary {
+  padding: 0;
+}
+.collapse-processed .details-title {
+  display: block;
+  padding: 0.75em 1.25em;
+}

 /**
  * Form elements.