Securities - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	May. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Proceeds from Sale of Available-for-sale Securities, Debt		$ 60,314,000	$ 21,527,000	$ 67,330,000
Available-for-sale Securities, Gross Realized Gains		633,000	456,000	792,000
Available-for-sale Securities, Gross Realized Losses		$ 472,000		373,000
Collateral Underlying Mortgage Investments Terms		30- and 15-year fixed and 10/1 adjustable rate mortgage
Federal Home Loan Bank Stock and Federal Reserve Bank Stock		$ 16,400,000
Cost Method Investments, Fair Value Disclosure		16,400,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		698,059,000	527,782,000
Accumulated unrealized losses		12,703,000	10,026,000
Securities Available For Sale Transferred To Held-To-Maturity	$ 158,800,000	80,800,000
Available For Sale Securities Transferred To Held To Maturity Securities Unrealized Gain Loss	$ 3,100,000	0	(3,137,000)	$ 724,000
Trading Securities, Unrealized Holding Loss		2,300,000	2,800,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		443,830,000	301,140,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		$ 6,030,000	$ 3,672,000
Common Stock, Shares, Outstanding		34,351,409	33,136,592
Debt Instrument, Convertible, Conversion Price		$ 1.6483
Common Class B [Member]
Schedule of Available-for-sale Securities [Line Items]
Common Stock, Shares, Outstanding		11,330
Common Class A [Member]
Schedule of Available-for-sale Securities [Line Items]
Stock Issued During Period, Shares, Conversion of Convertible Securities		18,675
Available-for-sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		$ 1,200,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value		38,900,000	$ 32,300,000
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss		400,000	$ 300,000
Carrying Amount [Member] | Repurchase Agreement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral		172,000,000
Carrying Amount [Member] | United States Treasury Deposits and Other Public and Trust Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral		171,900,000
Fair Value [Member] | Repurchase Agreement [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral		172,000,000
Fair Value [Member] | United States Treasury Deposits and Other Public and Trust Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Securities pledged as collateral		172,800,000
Mortgage Backed Securities And Collateralized Mortgage Obligations Of Us Government Sponsored Entities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		371,500,000
Accumulated unrealized losses		6,600,000
Collateralized Loan Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		162,500,000
Accumulated unrealized losses		3,300,000
Private Collateralized Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value		83,300,000
Accumulated unrealized losses		$ 1,600,000