Subsequent Events (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions								1 Months Ended	2 Months Ended	3 Months Ended								12 Months Ended
	Jan. 27, 2016	Oct. 22, 2015	Jul. 23, 2015	Apr. 23, 2015	Jan. 27, 2015	Oct. 23, 2014	Jul. 22, 2014	Jan. 31, 2016	Feb. 19, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Cash dividends declared per share of common stock (in dollars per share)		$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10			$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0.10	$ 0	$ 0	$ 0.40	$ 0.20	$ 0
Repurchases under stock repurchase programs, average price (in dollar per share)																		$ 25.16	$ 22.42	$ 19.76
Stock Repurchase Program 2014 [Member]
Subsequent Event [Line Items]
Stock repurchase program, remaining authorized repurchase amount										$ 532.5								$ 532.5
Subsequent Event [Member] | Stock Repurchase Program 2014 [Member]
Subsequent Event [Line Items]
Common stock repurchased									3.1
Common stock repurchased, value									$ 75.0
Repurchases under stock repurchase programs, average price (in dollar per share)									$ 23.89
Stock repurchase program, remaining authorized repurchase amount									$ 457.5
Subsequent Event [Member] | First Quarter of 2015 [Member]
Subsequent Event [Line Items]
Cash dividends declared per share of common stock (in dollars per share)	$ 0.10
Subsequent Event [Member] | BTI Systems, Inc [Member]
Subsequent Event [Line Items]
Consideration transferred								$ 65.0