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,

	2011		2012
Numerator:
Net income (controlling interest)	$	39.1	$	37.4

Denominator:
Average shares outstanding—basic		51.8		51.6
Effect of dilutive instruments:
Stock options and other awards		1.3		1.3

Average shares outstanding—diluted		53.1		52.9

As more fully discussed in Note 3, the Company had convertible securities outstanding during the periods presented and is required to apply the if-converted method to these securities in its calculation of diluted earnings per share. Under the if-converted method, shares that are issuable upon conversion are deemed outstanding, regardless of whether the securities are contractually convertible into the Company's common stock at that time. For this calculation, the interest expense (net of tax) attributable to these dilutive securities is added back to Net income (controlling interest), reflecting the assumption that the securities have been converted. Issuable shares for these securities and related interest expense are excluded from the calculation if an assumed conversion would be anti-dilutive to diluted earnings per share.

For the three months ended March 31, 2012, the Company repurchased approximately 0.3 million shares of common stock under the share repurchase programs approved by the Company's Board of Directors.

The diluted earnings per share calculations in the table above exclude the anti-dilutive effect of the following shares:

	For the Three Months Ended March 31,

	2011		2012
Stock options and other awards		0.6		1.2
Senior convertible securities		4.2		4.2
Junior convertible trust preferred securities		3.7		3.7

As discussed further in Note 16, 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 repurchases in cash, the calculation of diluted earnings per share excludes any potential dilutive effect from possible share settlements.