Few months ago Google had launched their backup service called Google Takeout, it allows you to download a backup copy in ZIP format to your computer.
Now Google Takeout support Google Docs, means you can download a copy of all your doc files right on to your computer.
To download your Doc files, login to Google Takeout using your Google Account, now click on Choose Service and then click on Docs, then it will show you the number of files in your account and its size.
At last click on Create Archive and then download your zip file. You can download all your service data too, just click on All Of Your data tab and then click on Click Archive to download them.
You can also define the file format you wanna download, like you wanna download Documents in MS Word form or Rich or so on, for this click on Configure.