Loans and Allowance for Loan Losses - TDRs and the pre and post-modification recorded investment (Details 6) (Loans Receivable, USD $) In Thousands, unless otherwise specified	Mar. 31, 2013 Contract	Dec. 31, 2012 Contract	Mar. 31, 2012 Contract
Financing Receivable, Modifications [Line Items]
Number of Contracts	400	388	336
Pre-Modification Outstanding Recorded Investment	$ 171,887	$ 172,727	$ 165,087
Post-Modification Outstanding Recorded Investment	158,760	160,763	158,507
Residential mortgage
Financing Receivable, Modifications [Line Items]
Number of Contracts	120	117	99
Pre-Modification Outstanding Recorded Investment	19,901	20,323	15,718
Post-Modification Outstanding Recorded Investment	19,023	19,296	14,832
Residential construction
Financing Receivable, Modifications [Line Items]
Number of Contracts	71	67	63
Pre-Modification Outstanding Recorded Investment	25,651	25,822	27,128
Post-Modification Outstanding Recorded Investment	23,345	23,786	25,948
Consumer installment
Financing Receivable, Modifications [Line Items]
Number of Contracts	46	51	40
Pre-Modification Outstanding Recorded Investment	282	1,292	340
Post-Modification Outstanding Recorded Investment	269	1,282	330
Commercial Portfolio Segment
Financing Receivable, Modifications [Line Items]
Number of Contracts	163	153	134
Pre-Modification Outstanding Recorded Investment	126,053	125,290	121,901
Post-Modification Outstanding Recorded Investment	116,123	116,399	117,397
Commercial Portfolio Segment | Commercial (secured by real estate)
Financing Receivable, Modifications [Line Items]
Number of Contracts	97	96	92
Pre-Modification Outstanding Recorded Investment	80,618	80,261	83,230
Post-Modification Outstanding Recorded Investment	74,675	75,340	79,844
Commercial Portfolio Segment | Commercial & industrial
Financing Receivable, Modifications [Line Items]
Number of Contracts	41	32	26
Pre-Modification Outstanding Recorded Investment	8,944	7,492	3,487
Post-Modification Outstanding Recorded Investment	8,834	7,250	3,487
Commercial Portfolio Segment | Commercial construction
Financing Receivable, Modifications [Line Items]
Number of Contracts	25	25	16
Pre-Modification Outstanding Recorded Investment	36,491	37,537	35,184
Post-Modification Outstanding Recorded Investment	$ 32,614	$ 33,809	$ 34,066