Stockholders' Equity - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2016	Sep. 30, 2015
Equity [Abstract]
Cash dividends declared per common share (in dollars per share)	$ 0.16	$ 0.16	$ 0.16	$ 0.155	$ 0.155	$ 0.155	$ 0.48	$ 0.465
Equity [Abstract]
Remaining amount available under share repurchase authorization	$ 309.7						$ 309.7
Stock repurchased and retired, publicly announced authorizations, average cost excluding commissions (in dollars per shares)							$ 19.22	$ 20.12
Stock repurchased and retired, publicly announced authorizations, value excluding commissions							$ 402.2	$ 431.2
Stock repurchased and retired, publicly announced authorizations (in shares)							20.9	21.4
Cash Dividends Paid	$ 77.7	$ 78.1	$ 79.3	$ 78.5	$ 79.5	$ 80.5	$ 235.1	$ 238.5