Stockholders' Equity (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of common stock activity
Shares outstanding at the beginning of the year	18.5	18.1	18.0
Stock grants to employees	0.0	0.2	0.1
401k Performance contribution	0.0	0.2	0.0
Employee stock purchases	0.1	0.1	0.1
Shares relinquished	(0.1)	(0.1)	(0.1)
Shares outstanding at the end of the year	18.5	18.5	18.1