Consolidated Statements of Stockholder's Equity (Parenthetical) - shares shares in Millions	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Stockholders' Equity [Roll Forward]
Exercise of employee stock options (in shares)	0.2	0.3
Business acquisitions (in shares)		1.4

Number of share options (or share units) exercised during the current period.

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Balance Type:	na
Period Type:	duration