Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2011

Earnings Per Share [Abstract]

Computation of basic and diluted net income per common share

	2011		2010		2009
Numerator:
Net income	$	110.8	$	80.8	$	81.4
Numerator for basic earnings per share — income available to common shareholders	$	110.8	$	80.8	$	81.4
Effect of dilutive securities:
After-tax interest expense on convertible securities		—		0.2		1.3
Numerator for diluted earnings per share — income available to common shareholders	$	110.8	$	81.0	$	82.7
Denominator:
Denominator for basic earnings per share — weighted average shares		46.4		46.1		46.6
Effect of dilutive securities:
Equity compensation plans		0.7		0.5		0.4
Convertible preferred stock		0.1		0.1		0.1
Convertible securities		—		0.3		1.7
Denominator for diluted earnings per share — adjusted weighted average and assumed conversion		47.2		47.0		48.8
Basic earnings per share	$	2.39	$	1.75	$	1.74
Diluted earnings per share	$	2.35	$	1.72	$	1.70