Securities (Additional Information) (Details)	3 Months Ended	12 Months Ended
	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($) security	Dec. 31, 2014 USD ($) security	Dec. 31, 2013 USD ($)
Schedule of Investments [Line Items]
Unrealized gains on securities available-for-sale included in accumulated other comprehensive income, net of deferred taxes		$ (3,801,000)	$ (319,000)
Unrealized gains on securities available-for-sale included in accumulated other comprehensive income, deferred taxes		$ 2,047,000	$ 171,000
Number of investment securities which had unrealized losses for twelve months or longer | security		109	74
AFS and HTM securities in Continues Unrealized Loss Position		$ 546,000,000	$ 434,100,000
AFS and HTM Securities Unrealized Loss Accumulated in Investments		10,200,000	7,900,000
Investment securities with unrealized losses for twelve months or longer		192,809,000	307,951,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		6,709,000	7,313,000
Investment securities with unrealized losses that are considered temporary		540,460,000	428,315,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments		(10,141,000)	(7,924,000)
Other than temporary impairment losses			0
Federal Home Loan Bank Stock		20,600,000	19,500,000
Federal Reserve Bank Stock		908,000	891,000
Carrying value of investments sold		12,400,000	25,200,000	$ 16,800,000
Security pledged as collateral, amortized cost		577,600,000	486,200,000
Security pledged as collateral, fair value		$ 570,900,000	$ 485,600,000
Unrealized Loss as a Percent of Amortized Cost		2.00%	2.00%
Gross realized gains		$ 221,000	$ 451,000	785,000
Mortgage Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Investment securities with unrealized losses for twelve months or longer		192,800,000	308,000,000
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss		6,700,000	7,300,000
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Investment Securities Sold, Carrying Amount	$ 7,300,000
Private issue collateralized mortgage obligations [Member]
Schedule of Investments [Line Items]
Investment securities with unrealized losses for twelve months or longer			0
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss			0
Investment securities with unrealized losses that are considered temporary			1,785,000
Available For Sale Securities Continuous Unrealized Loss Position Aggregate Losses Accumulated In Investments			(8,000)
Other than temporary impairment losses		204,000
Available-for-sale Securities [Member]
Schedule of Investments [Line Items]
Unrealized gains on securities available-for-sale included in accumulated other comprehensive income, deferred taxes		2,047,000	171,000
Realized Investment Gains (Losses)		$ 4,000
Gross realized gains			$ 451,000	$ 785,000