Stockholders' Equity (Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Stockholders' Equity [Line Items]
Cash dividends declared	$ 0	$ 0	$ 0	$ 0
Remaining shares of common stock available for purchase (in shares)	15,900,000		15,900,000
Cumulative Number Of Shares Authorized For Repurchase
Stockholders' Equity [Line Items]
Authorized stock repurchase (in shares)	90,000,000		90,000,000
Share Repurchase Program
Stockholders' Equity [Line Items]
Value of common stock repurchased			$ 50.6	$ 149.3