Commitments and Contingencies (Details 2) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended		1 Months Ended	2 Months Ended	9 Months Ended	12 Months Ended
	Jul. 24, 2013	Oct. 25, 2011	Oct. 21, 2013	Dec. 31, 2011	Sep. 30, 2013	Dec. 31, 2012
Commitments and Contingencies
Amount authorized under stock repurchase plan	$ 300	$ 200
Share repurchases made in open market (in shares)			0	671,776	955,776	459,252
Average price of shares repurchased (in dollars per share)				$ 48.72	$ 50.23	$ 50.27
Aggregate cost of shares repurchased, excluding broker commissions				32.7	48.0	23.1
Remaining authorized repurchase amount					$ 196.2