Fair Value of Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Fair Value of Financial Instruments
Cost to assume off-balance sheet commitments and standby letters of credit as a percentage of notional amount	10.00%
Assets:
Securities available for sale	$ 301,160	$ 150,739	$ 84,066
Federal Reserve Bank and FHLB stock, at cost	10,974	11,975	11,247
Other real estate owned	1,561	1,768	2,258
Accrued interest receivable	4,898	3,632	4,126
Off-balance sheet commitments and standby letters of credit
Notional Amount	236,720	105,011	131,450
Cost to Cede or Assume	23,672	10,501	13,145
Level 1
Assets:
Cash and cash equivalents	99,458	93,649	59,352
Securities available for sale	142,219	146,875	81,042
Federal Reserve Bank and FHLB stock, at cost	10,974	11,975	11,247
Accrued interest receivable	4,898	3,632	4,126
Liabilities:
Deposit accounts	835,196	436,064	548,101
FHLB advances			87,000
Accrued interest payable	213	181	142
Level 2
Assets:
Securities available for sale	157,957	2,898	2,072
Loans held for sale, net	3,643	62	3,681
Liabilities:
Deposit accounts	351,462	413,314	363,382
Other borrowings	47,463	31,964	31,267
Subordinated debentures	4,865	7,617	4,973
Off-balance sheet commitments and standby letters of credit
Cost to Cede or Assume	23,672	10,501	13,145
Level 3
Assets:
Securities available for sale	984	966	952
Loans held for investment, net	1,004,001	758,893	1,049,589
Carrying Amount
Assets:
Cash and cash equivalents	99,458	93,649	59,352
Securities available for sale	301,160	150,739	84,066
Federal Reserve Bank and FHLB stock, at cost	10,974	11,975	11,247
Loans held for sale, net	3,643	62	3,681
Loans held for investment, net	933,834	687,079	974,213
Accrued interest receivable	4,898	3,632	4,126
Liabilities:
Deposit accounts	1,185,719	846,717	904,768
FHLB advances			87,000
Other borrowings	44,191	28,500	28,500
Subordinated debentures	10,310	10,310	10,310
Accrued interest payable	213	181	142
Estimated Fair Value
Assets:
Cash and cash equivalents	99,458	93,649	59,352
Securities available for sale	301,160	150,739	84,066
Federal Reserve Bank and FHLB stock, at cost	10,974	11,975	11,247
Loans held for sale, net	3,643	62	3,681
Loans held for investment, net	1,004,001	758,893	1,049,589
Accrued interest receivable	4,898	3,632	4,126
Liabilities:
Deposit accounts	1,186,658	849,378	911,483
FHLB advances			87,000
Other borrowings	47,463	31,964	31,267
Subordinated debentures	4,865	7,617	4,973
Accrued interest payable	$ 213	$ 181	$ 142