diff --git a/packages/common/src/directives/ng_style.ts b/packages/common/src/directives/ng_style.ts
index fa41226bc7..b7861dddea 100644
--- a/packages/common/src/directives/ng_style.ts
+++ b/packages/common/src/directives/ng_style.ts
@@ -34,8 +34,9 @@ import {Directive, DoCheck, ElementRef, Input, KeyValueChanges, KeyValueDiffer,
  * @description
  *
  * An attribute directive that updates styles for the containing HTML element.
- * Sets one or more style properties, specified as key-value pairs.
- * The key is a style name, with an optional `.<unit>` suffix (such as 'top.px', 'font-style.em').
+ * Sets one or more style properties, specified as colon-separated key-value pairs.
+ * The key is a style name, with an optional `.<unit>` suffix
+ * (such as 'top.px', 'font-style.em').
  * The value is an expression to be evaluated.
  * The resulting non-null value, expressed in the given unit,
  * is assigned to the given style property.
@@ -54,13 +55,24 @@ export class NgStyle implements DoCheck {
       private _differs: KeyValueDiffers, private _ngEl: ElementRef, private _renderer: Renderer2) {}
 
   @Input()
-  set ngStyle(values: {[key: string]: string}) {
+  set ngStyle(
+      /**
+       * An array of style properties, specified as colon-separated
+       * key-value pairs.
+       * * The key is a style name, with an optional `.<unit>` suffix
+       *    (such as 'top.px', 'font-style.em').
+       * * The value is an expression to be evaluated.
+       */
+      values: {[key: string]: string}) {
     this._ngStyle = values;
     if (!this._differ && values) {
       this._differ = this._differs.find(values).create();
     }
   }
 
+  /**
+   * Applies the new styles if needed.
+   */
   ngDoCheck() {
     if (this._differ) {
       const changes = this._differ.diff(this._ngStyle);