its results. American Express shares had ended regular trading at $87.78, down 0.5 percent.
During the regular session, UnitedHealth Group Inc fell 2.8 percent to close at $72.76 after the largest US health insurer said that implementing the national healthcare reform law, often called Obamacare, and funding cuts for private Medicare coverage would result in expenses that would eat into 2014 profit. UnitedHealth, however, reported a higher fourth-quarter profit on Thursday and said 2014 earnings would improve.
Shares of UnitedHealth's major competitors fell as well, including Aetna Inc, down 1.6 percent at $70.23.
CSX Corp shares sank 6.8 percent to $27.24 a day after the US railroad reported profits that missed expectations.
The stock of Best Buy Co Inc plunged 28.6 percent to close at $26.83, making it easily the S&P 500's biggest percentage decliner, followed by CSX. Best Buy, the world's largest consumer electronics chain, reported a drop in holiday sales and forecast a bigger-than-expected decline in quarterly operating margins.
The day's economic data included initial claims for state unemployment benefits, which slipped 2,000 to a seasonally adjusted 326,000 in the week ended Jan. 11. Claims for the prior week were revised to show 2,000 fewer applications received than previously reported, suggesting a sharp slowdown in job growth in December was likely to be temporary.
The Consumer Price Index rose 0.3 percent in December while the core CPI, which strips out volatile food and energy prices, edged up only 0.1 percent, suggesting underlying inflation was muted. The Philadelphia Federal Reserve Bank said its business activity index stood at 9.4 points in January, compared with 6.4 in December.
In the deal arena, Apollo Global Management LLC said it would buy CEC Entertainment Inc, the parent of the Chuck E Cheese restaurant chain, for about $948 million. CEC Entertainment's stock jumped 13.1 percent to $54.75. Apollo Global's shares rose 0.8 percent to end at $36.05.
Volume was slightly below the average for the month. About 6.4 billion shares changed hands on US exchanges, compared with the average of 6.6 billion so far this month, according to data from BATS Global Markets.
Advancers outnumbered decliners on the New York Stock Exchange by a ratio of about 17 to 12. On the Nasdaq, advancers were about even with decliners.