Earnings Per Share (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Jun. 30, 2014
Earnings Per Share [Abstract]
Stock Repurchase Program, Authorized Amount	$ 300,000,000		$ 250,000,000
Stock Repurchased During Period, Shares	1,200,000.0
Treasury Stock, Value, Acquired, Cost Method	$ 50,000,000
Numerator:
Net income	$ 69,300,000	$ 62,200,000
Denominator:
Denominator for basic earnings per share — weighted average shares	41,400,000	44,100,000
Effect of dilutive securities:
Equity compensation plans	400,000	700,000
Denominator for diluted earnings per share — adjusted weighted average and assumed conversion	41,800,000	44,800,000
Basic earnings per share (in dollars per share)	$ 1.67	$ 1.41
Diluted earnings per share (in dollars per share)	$ 1.66	$ 1.39