Earnings Per Share (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Mar. 31, 2014
Earnings Per Share [Abstract]
Stock Repurchase Program, Authorized Amount					$ 250,000,000
Stock Repurchased During Period, Shares			1,900,000.0
Payments for Repurchase of Common Stock			124,600,000	50,000,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	125,400,000		125,400,000
Numerator:
Net income	$ 51,300,000	$ 53,800,000	$ 146,500,000	$ 116,000,000
Denominator:
Denominator for basic earnings per share — weighted average shares	44,400,000	46,200,000	45,300,000	46,500,000
Effect of dilutive securities:
Equity compensation plans	800,000	600,000	800,000	700,000
Convertible preferred stock	0		0
Denominator for diluted earnings per share — adjusted weighted average and assumed conversion	45,200,000	46,800,000	46,100,000	47,200,000
Basic earnings per share (in dollars per share)	$ 1.16	$ 1.16	$ 3.24	$ 2.49
Diluted earnings per share (in dollars per share)	$ 1.14	$ 1.15	$ 3.18	$ 2.45