Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 13, 2015	Oct. 19, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Oct. 21, 2015
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared			$ 0.40	$ 0.35	$ 1.20	$ 1.05
Repayments of Unsecured Debt					$ 6.1	$ 0.0
Subsequent Event
Subsequent Event [Line Items]
Common Stock, Dividends, Per Share, Declared	$ 0.40
Cash dividends declared	$ 7.1
Subsequent Event | Warrant Transactions
Subsequent Event [Line Items]
Exercise price per share of Warrants		$ 60.32					$ 60.20
Warrant Transactions | Subsequent Event
Subsequent Event [Line Items]
Issuance of stock warrants		102,555
Shares owed and pending settlement		8,200
Senior Notes
Subsequent Event [Line Items]
Repayments of Unsecured Debt			$ 6.1
Senior Notes | Subsequent Event
Subsequent Event [Line Items]
Percentage of principal amount repurchased		107.50%
Repayments of Unsecured Debt		$ 21.1