Earnings Per Common Share Offerings (Details)			12 Months Ended
	Feb. 13, 2013 shares	Sep. 19, 2012 USD ($) Tangible_Equty_Unit $ / shares shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 shares	Dec. 31, 2013 shares
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares—Basic			56,734,000	55,305,000	53,788,000
Class A Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock issued during period, shares		3,791,004
Shares Issued, Price Per Share | $ / shares		$ 64.75
Conversion of shares to Class A Common Stock, shares	5,984,232
Settlement of the prepaid stock purchase contract component of the TEUs [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Weighted average shares—Basic			3,539,240	2,841,650	2,800,000
Underwriter's exercise of over-allotment option [Member] | Class A Common Stock [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] | Class A Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
TEUs Issued During Period, TEUs, New Issues | Tangible_Equty_Unit		2,300,000
TEUs, Stated Amount, Per Unit Value | $		$ 100
Tangible Equity Units [Member] | Underwriter's exercise of over-allotment option [Member] | Class A Common Stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
TEUs Issued During Period, TEUs, New Issues | Tangible_Equty_Unit		300,000
TEUs - amortizing note [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
TEUs Issued During Period, TEUs, New Issues | Tangible_Equty_Unit		2,300,000
TEUs, Stated Amount, Per Unit Value | $		$ 100
Repayments of Debt | $			$ 2,800,000