Consolidated Statements of Operations (Unaudited) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Income Statement [Abstract]
Revenues from services	$ 4,757.2	$ 4,587.7
Cost of services	3,969.4	3,813.9
Gross profit	787.8	773.8
Selling and administrative expenses	660.8	642.1
Operating profit	127.0	131.7
Interest and other expenses	14.9	12.7
Earnings before income taxes	112.1	119.0
Provision for income taxes	37.7	47.3
Net earnings	$ 74.4	$ 71.7
Net earnings per share - basic (in dollars per share)	$ 1.10	$ 0.98
Net earnings per share - diluted (in dollars per share)	$ 1.09	$ 0.98
Weighted average shares - basic (in shares)	67.7	72.8
Weighted average shares - diluted (in shares)	68.4	73.5