Loans and Allowance for Loan Losses (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($) loan	Mar. 31, 2015 USD ($) loan	Dec. 31, 2015 USD ($)		Dec. 31, 2014 USD ($)
Financing Receivable [Line Items]
Net loan premiums	$ 3,400		$ 3,700
Unpaid principal balance of loans serviced to others	361,400		304,600
Loans pledged to collateralize FHLB advances and letters of credit	97,300		102,900
Investment securities pledged to collateralize FHLB advances and letters of credit	112,600		113,000
Credit availability for borrowing under FHLB advances and letters of credit	108,400		80,800
Loans pledged to collateralize potential borrowings from Federal Reserve Discount Window	4,100
Securities pledged to collateralize potential borrowings from Federal Reserve Discount Window	43,800
Borrowing capacity under Federal Reserve Discount Window	46,800
Additional borrowings from FHLB	302,700
Interest lost on nonaccrual loans	300	$ 400
Loans on nonaccrual status	18,400		18,000
Restructured loans	17,100		17,900
Allowance of loan losses	14,240	19,008	$ 15,195	[1]	$ 20,345
Charge-offs	1,094	994
Recoveries	674	794
Net charge-offs	$ 420	$ 200
ALL, as a percentage of loans held for investment	0.93%	1.36%	0.98%
Number of loans | loan	2	0
Reserve for unfunded commitments	$ 900		$ 800
Letter of Credit [Member]
Financing Receivable [Line Items]
Expected usage percentage of remaining unfunded commitments	10.00%
Granite Corp [Member]
Financing Receivable [Line Items]
Loans purchased	$ 81,873	$ 106,068
Substandard or Doubtful [Member]
Financing Receivable [Line Items]
Loans purchased	21,000		27,000
Performing Financial Instruments [Member]
Financing Receivable [Line Items]
Restructured loans	12,000		13,100
PI loans [Member] | Granite Corp [Member]
Financing Receivable [Line Items]
Allowance of loan losses	2,800		2,800
PC and Originated Loans [Member] | Granite Corp [Member]
Financing Receivable [Line Items]
Allowance of loan losses	$ 300		$ 300

[1] Derived from audited consolidated financial statements