Supplementary Data Share Repurchase Program (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 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	4.8	5.0
Aggregate cost, including fees	$ 115.0	$ 112.5
Average price per share, including fees	$ 24.13	$ 22.47
Stock repurchase program, remaining authorized repurchase amount, excluding fees	$ 340.4