Earnings Per Share

The calculation of basic earnings per share is based on the weighted average number of shares of the Company’s common stock outstanding during the period. Diluted earnings per share is similar to basic earnings per share, but adjusts for the dilutive effect of the potential issuance of incremental shares of the Company’s common stock. The following is a reconciliation of the numerator and denominator used in the calculation of basic and diluted earnings per share available to common stockholders:



	For the Three Months Ended March 31,
	2017		2018
Numerator
Net income (controlling interest)	$	122.5	$	153.0
Interest expense on convertible securities, net of taxes	3.8		4.7
Net income (controlling interest), as adjusted	$	126.3	$	157.7
Denominator
Average shares outstanding (basic)	56.7		54.6
Effect of dilutive instruments:
Stock options and restricted stock units	0.3		0.2
Convertible securities	2.2		2.2
Average shares outstanding (diluted)	59.2		57.0

Average shares outstanding (diluted) in the table above excludes share-based awards that have not satisfied performance conditions and the anti-dilutive effect of the following share-based awards:



	For the Three Months Ended March 31,
	2017	2018
Stock options and restricted stock units	0.2	0.1

The Company may settle portions of its Affiliate equity purchases in shares of its common stock. Because it is the Company’s intent to settle these potential purchases in cash, the calculation of diluted earnings per share excludes any potential dilutive effect from possible share settlements of Affiliate equity purchases.

In the three months ended March 31, 2018, the Company repurchased 0.8 million shares of its common stock at an average price per share of $192.70.