Accounting Policies and Basis of Presentation Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014 branch	Dec. 31, 2012	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Period fair values are subject to refinement	1 year
Number of branches	572
Net deferred fees on non-PCI loans	$ 20,800,000		$ 22,900,000
Baseline for measurement	500,000
Securities sold under repurchase agreements	294,400,000		97,000,000
Cumulative effect of the retrospective application of the change in amortization method		(2,430,000)
Class A Common Stock
Property, Plant and Equipment [Line Items]
Votes per share of common stock	1
Class B Common Stock
Property, Plant and Equipment [Line Items]
Votes per share of common stock	16
Premises | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	25 years
Premises | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	40 years
Furniture, Software, and Equipment | Minimum
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	3 years
Furniture, Software, and Equipment | Maximum
Property, Plant and Equipment [Line Items]
Estimated useful life of asset	10 years
Shares and Cash
Property, Plant and Equipment [Line Items]
Right to receive cash per share	50.00
Shares and Cash | Class A Common Stock
Property, Plant and Equipment [Line Items]
Right to receive number of shares conversion	4.00
Shares Only | Class A Common Stock
Property, Plant and Equipment [Line Items]
Right to receive number of shares conversion	3.58
Shares Only | Class B Common Stock
Property, Plant and Equipment [Line Items]
Right to receive number of shares conversion	0.42
Retained Earnings [Member]
Property, Plant and Equipment [Line Items]
Cumulative effect of the retrospective application of the change in amortization method		$ (2,430,000)