Earnings Per Common Share Offerings (Details) (Class A Common Stock [Member], USD $)	0 Months Ended	12 Months Ended
	Sep. 19, 2012	Dec. 31, 2012	Sep. 28, 2012	Oct. 02, 2015
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock issued during period, shares	3,791,004	3,791,004
Shares Issued, Price Per Share	$ 64.75
Share price			$ 66.86
Underwriter's exercise of over-allotment option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock issued during period, shares	525,000
Tangible Equity Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
TEUs Issued During Period, TEUs, New Issues	2,300,000
TEUs, Stated Amount, Per Unit Value	$ 100
Tangible Equity Units [Member] | Underwriter's exercise of over-allotment option [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
TEUs Issued During Period, TEUs, New Issues	300,000
Minimum [Member] | Scenario, Forecast [Member] | Tangible Equity Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share price				$ 80.94
Tangible Equity Units Number Of Shares Upon Conversion Per Unit				1.2355
Maximum [Member] | Scenario, Forecast [Member] | Tangible Equity Units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Share price				$ 64.75
Tangible Equity Units Number Of Shares Upon Conversion Per Unit				1.5444