Aetna's board of directors approved on Friday an additional $750 million to repurchase the company's common stock at some point in the future.

The buybacks will take place "from time to time." Added to the $248 million that Aetna had on hand that was already approved for repurchases as of June 30, the company now has nearly $1 billion to buy its shares.

The Hartford-based health insurer repurchased about $580 million worth of stock during the second quarter, from April 1 through June 30.

Shares of the company were trading at $36.96, up 29 cents Monday morning. The company has 347.4 million shares outstanding and a market cap of $12.8 billion.