Supplementary Data Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Feb. 10, 2017	Feb. 12, 2016
Disclosure of Repurchase Agreements [Abstract]
Stock repurchase program, authorized amount			$ 300.0	$ 300.0
Number of shares repurchased	2.3	2.5
Aggregate cost, including fees	$ 55.0	$ 53.7
Average price per share, including fees	$ 23.85	$ 21.67
Stock repurchase program, remaining authorized repurchase amount, excluding fees	$ 400.4