Earnings per Share - Computation of EPS (Details) - shares shares in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Reconciliation of the weighted-average number of common shares used to compute basic earnings per share (EPS) to those used to compute diluted EPS
Weighted-average number of common shares outstanding-basic (in shares)	64.3	64.2	64.3	64.1
Add: Effect of dilutive share-based compensation awards (in shares)	0.0	0.0	0.0	0.0
Weighted-average number of shares-diluted (in shares)	64.3	64.2	64.3	64.1