Earnings per Share Weighted Average Dilutive Shares and Offerings (Details) (USD $)	3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended						3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2013 Tangible Equity Units [Member]	Sep. 30, 2012 Tangible Equity Units [Member]	Jun. 30, 2013 Tangible Equity Units [Member]	Sep. 19, 2012 Tangible Equity Units [Member]	Oct. 02, 2015 Tangible Equity Units [Member] Maximum [Member]	Jun. 30, 2013 Tangible Equity Units [Member] Maximum [Member]	Oct. 02, 2015 Tangible Equity Units [Member] Minimum [Member]	Jun. 30, 2013 Tangible Equity Units [Member] Minimum [Member]	Jun. 30, 2013 Class A common shares [Member]	Sep. 30, 2012 Class A common shares [Member]	Jun. 30, 2013 Class A common shares [Member]	Sep. 19, 2012 Class A common shares [Member]
Schedule of Stock Offering [Line Items]
Weighted average share impact resulting from offerings			2,841,650		2,841,650						3,791,004		3,791,004
Weighted average share impact from the conversion of Series A-1 Preferred Stock	5,984,232	4,529,502
Stock Issued During Period, Shares, New Issues				2,300,000								3,791,004
Sale of stock, price per share														$ 64.75
Shares issued as a result of the underwriter's exercise of their over-allotment option				300,000								525,000
Stated par value per share						$ 100
Share Price								$ 64.75		$ 80.94
Tangible Equity Units Number Of Shares Upon Conversion Per Unit							1.5444		1.2355