The Federal Reserve decided not to raise interest rates, because of the lack of inflation, economic slowdown and global unrest.  As expected the USD fell in value, but what was unexpected is the market went down when normally it would have gone up knowing that interest rates were not going up.  The emerging markets all breathed a sigh of relief, because had interest rates gone up, their debt payments would have increased as well since the US comprises 63% of most of the loans from the World Bank and IMF.

Treasuries Rally Dollar Falls as Fed Stands Pat Stocks Slide (9-17-15)
http://www.bloomberg.com/news/articles/2015-09-16/asian-futures-jump-as-fed-day-looms-while-crude-extends-advance

Fed Leave Rates Unchanged (9-17-15)
http://www.bloomberg.com/news/articles/2015-09-17/fed-leaves-interest-rates-unchanged-at-zero-0-25-target-range

Federal Open Market Committee Sept 17 Statement Text (9-17-15)
http://www.bloomberg.com/news/articles/2015-09-17/federal-open-market-committee-sept-17-statement-text

Yellen’s Decision to Delay Fed Liftoff Points to Global Risks (9-17-15)
http://www.bloomberg.com/news/articles/2015-09-17/yellen-s-decision-to-delay-fed-liftoff-points-to-global-risks