Earnings Per Share (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Jan. 29, 2016	Jun. 30, 2014
Earnings Per Share [Abstract]
Stock Repurchase Program, Authorized Amount					$ 300,000,000	$ 250,000,000
Stock Repurchased During Period, Shares			2,200,000.0
Treasury Stock, Value, Acquired, Cost Method			$ 95,000,000
Numerator:
Net income	$ 95,700,000	$ 39,500,000	$ 226,200,000	$ 147,100,000
Denominator:
Denominator for basic earnings per share — weighted average shares	40,100,000	42,800,000	40,700,000	43,500,000
Effect of dilutive securities:
Equity compensation plans	500,000	600,000	500,000	600,000
Denominator for diluted earnings per share — adjusted weighted average and assumed conversion	40,600,000	43,400,000	41,200,000	44,100,000
Basic earnings per share (in dollars per share)	$ 2.39	$ 0.92	$ 5.55	$ 3.38
Diluted earnings per share (in dollars per share)	$ 2.36	$ 0.91	$ 5.49	$ 3.33