Seattle-based Internet retailer Amazon.com said Thursday it completed a bond offering for $3 billion.

Amazon announced the offering Monday, saying proceeds will be used for general corporate purposes, including the $1.16 billion purchase of its leased Seattle headquarters.

Amazon, which held $5.2 billion in cash and marketable securities at the end of September, said it made a non-refundable deposit of $51 million and expects to finalize the deal in the fourth quarter.

Analysts say fast-growing Amazon is taking advantage of low borrowing costs to prop up its cash pile.

Amy Martinez: 206-464-2923 or amartinez@seattletimes.com