India's SBI Life Insurance Co Ltd, a unit of State Bank of India (SBI.NS), on Monday filed for an initial public offering of shares that bankers have said could raise more than $1 billion.SBI, the nation's top bank by assets, is selling up to 8 percent stake, or 80 million shares, in the unit as part of the IPO, while BNP Paribas Cardif is selling up to 4 percent stake, or 40 million shares, according to a regulatory filing.The filing did not mention how much the IPO would raise, although bankers have previously said it would likely raise more than $1 billion.SBI Life, which is 70 percent owned by SBI and 26 percent by BNP Paribas Cardif, will not receive any proceeds from the IPO.