Subsequent Events Subsequent Event (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended				9 Months Ended			1 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 18, 2014	Mar. 07, 2013	Sep. 30, 2014 Tender Offer [Member]		Sep. 30, 2013 Tender Offer [Member]	Oct. 20, 2014 Tender Offer [Member] Subsequent Event [Member]	Sep. 19, 2014 Tender Offer [Member] Subsequent Event [Member]
Subsequent Event [Line Items]
Increase in number of shares authorized for repurchase					995,698	1,000,000					995,698
Stock Repurchased During Period, Value Per Share										$ 126
Common stock repurchased, shares	0	282,018	1,691,046	1,145,701			1,553,170		0	995,698
Common stock repurchased, value	$ 0	$ 31.3	$ 218.7	$ 127.2			$ 200.3	[1]	$ 0	$ 125.0

[1] Tender Offer Cost amount includes offering costs of $0.3 million for the nine months ended September 30, 2014.