[["( in millions )", "years ended december 31 , 2015", "years ended december 31 , 2014", "years ended december 31 , 2013 ( 1 )"], ["basic weighted-average shares outstanding", "170.3", "170.6", "156.6"], ["effect of dilutive securities ( 2 )", "1.5", "2.2", "2.1"], ["diluted weighted-average shares outstanding ( 3 )", "171.8", "172.8", "158.7"]]