In 2014, the company grew to one million users, acquired the blockchain explorer service Blockr and the web bookmarking company Kippt, secured insurance covering the value of bitcoin stored on their servers, and launched the vault system for secure bitcoin storage. Throughout 2014, the company also formed partnerships with Overstock, Dell, Expedia, Dish Network, and Time Inc. allowing those firms to accept bitcoin payments. The company also added bitcoin payment processing capabilities to the traditional payment companies Stripe, Braintree, and PayPal.
The platform stores 98% of customers funds offline to ensure the security of the cryptocurrency assets you purchase and store within Coinbase. On their website, Coinbase assures customers that "sensitive data that would normally reside on our servers is disconnected entirely from the internet." Data is then encrypted, and transferred to USB drives and paper backups, and distributed in safe deposit boxes vaults all over the world.
The other 2% of customer funds, held online, are covered in the event of a breach of Coinbase's online storage. Also, Coinbase holds all customer fiat currency in custodial bank accounts, on behalf of customers. So, if you have fiat currency in Coinbase, in a USD wallet, it is covered by FDIC insurance up to $250,000 (just like a "regular" bank). This protects customer assets (so long as they have been converted to fiat currency) even in the event of Coinbase becoming insolvent.
If you do have this much money tied up in Bitcoin, though, you may want a more secure space to store it. If this is the case, Coinbase offers a Coinbase vault, which has time-delayed withdrawals (giving you 48 hours to cancel a withdrawal) and the option of multiple approvers, increasing security by ensuring that all withdrawals are approved by multiple people. They also offer a multisig vault, which is basically an even more involved and more secure vault, requiring multiple keys to unlock.