[["", "2012", "2011", "2010"], ["balance at beginning of year", "$ 48.1", "$ 50.9", "$ 55.2"], ["additions charged to expense", "29.7", "21.0", "23.6"], ["accounts written-off", "-32.5 ( 32.5 )", "-23.8 ( 23.8 )", "-27.9 ( 27.9 )"], ["balance at end of year", "$ 45.3", "$ 48.1", "$ 50.9"]]