This excerpt taken from the AMZN 10-K filed Jan 29, 2010.
Interest Income and Expense
Our interest income was $37 million, $83 million, and $90 million during 2009, 2008, and 2007. We generally invest our excess cash in investment grade short- to intermediate-term fixed income securities and AAA-rated money market funds. Our interest income corresponds with the average balance of invested funds and the prevailing rates we are earning on them, which vary depending on the geographies and currencies in which they are invested.
The primary component of our net interest expense is the interest we incur on our long-term debt instruments. Interest expense was $34 million, $71 million, and $77 million, in 2009, 2008, and 2007 with the decline primarily relating to principal reductions of $319 million in 2009 and $899 million in 2008.
Our long-term debt was $109 million and $409 million at December 31, 2009 and 2008. See Item 8 of Part II, Financial Statements and Supplementary DataNote 5Long-Term Debt.