Loans and Allowance for Credit Losses (Details 4) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Financing Receivable, Impaired [Line Items]
Average Recorded Investment			$ 120,600,000
Interest Income Recognized	2,600,000	2,200,000	566,000
Secured by 1-4 family
Financing Receivable, Impaired [Line Items]
Related Allowance		0
Construction
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance		0
Consumer
Financing Receivable, Impaired [Line Items]
Unpaid Principal Balance		313,000
With no related allowance recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	38,452,000	31,238,000
Unpaid Principal Balance	38,452,000	45,406,000
Related Allowance	0	0
Average Recorded Investment	36,202,000	34,086,000
Interest Income Recognized	677,000	291,000
With no related allowance recorded | Commercial | Business loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,938,000	1,716,000
Unpaid Principal Balance	2,938,000	10,378,000
Related Allowance	0	0
Average Recorded Investment	1,409,000	1,697,000
Interest Income Recognized	0	0
With no related allowance recorded | Construction | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	17,217,000	19,236,000
Unpaid Principal Balance	17,217,000	19,236,000
Related Allowance	0	0
Average Recorded Investment	18,571,000	19,315,000
Interest Income Recognized	677,000	291,000
With no related allowance recorded | Real estate | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	9,061,000	5,711,000
Unpaid Principal Balance	9,061,000	11,217,000
Related Allowance	0	0
Average Recorded Investment	7,944,000	7,064,000
Interest Income Recognized	0	0
With no related allowance recorded | Real estate | Commercial
Financing Receivable, Impaired [Line Items]
Recorded Investment	6,604,000	4,575,000
Unpaid Principal Balance	6,604,000	4,575,000
Related Allowance	0	0
Average Recorded Investment	6,451,000	5,111,000
Interest Income Recognized	0	0
With no related allowance recorded | Real estate | Secured by 1-4 family
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,632,000	0
Unpaid Principal Balance	2,632,000	0
Related Allowance	0
Average Recorded Investment	1,827,000	899,000
Interest Income Recognized	0	0
With no related allowance recorded | Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
With no related allowance recorded | Leases
Financing Receivable, Impaired [Line Items]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Average Recorded Investment	0	0
Interest Income Recognized	0	0
With an allowance recorded
Financing Receivable, Impaired [Line Items]
Recorded Investment	27,789,000	48,446,000
Unpaid Principal Balance	33,745,000	52,187,000
Related Allowance	3,930,000	5,271,000
Average Recorded Investment	30,160,000	36,951,000
Interest Income Recognized	0	0
With an allowance recorded | Commercial | Business loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	12,435,000	11,197,000
Unpaid Principal Balance	18,391,000	11,197,000
Related Allowance	2,983,000	3,124,000
Average Recorded Investment	15,484,000	11,056,000
Interest Income Recognized	0	0
With an allowance recorded | Construction | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	962,000	1,883,000
Unpaid Principal Balance	962,000	1,882,000
Related Allowance	14,000	298,000
Average Recorded Investment	321,000	1,916,000
Interest Income Recognized	0	0
With an allowance recorded | Real estate | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	11,439,000	30,533,000
Unpaid Principal Balance	11,439,000	34,275,000
Related Allowance	535,000	1,131,000
Average Recorded Investment	11,811,000	19,146,000
Interest Income Recognized	0	0
With an allowance recorded | Real estate | Commercial
Financing Receivable, Impaired [Line Items]
Recorded Investment	2,013,000	1,809,000
Unpaid Principal Balance	2,013,000	1,809,000
Related Allowance	89,000	271,000
Average Recorded Investment	671,000	730,000
Interest Income Recognized	0	0
With an allowance recorded | Real estate | Secured by 1-4 family
Financing Receivable, Impaired [Line Items]
Recorded Investment	763,000	2,279,000
Unpaid Principal Balance	763,000	2,279,000
Related Allowance	275,000	330,000
Average Recorded Investment	1,632,000	1,465,000
Interest Income Recognized	0	0
With an allowance recorded | Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	57,000	313,000
Unpaid Principal Balance	57,000
Related Allowance	16,000	52,000
Average Recorded Investment	59,000	310,000
Interest Income Recognized	0	0
With an allowance recorded | Leases
Financing Receivable, Impaired [Line Items]
Recorded Investment	120,000	432,000
Unpaid Principal Balance	120,000	432,000
Related Allowance	18,000	65,000
Average Recorded Investment	182,000	2,328,000
Interest Income Recognized	0	0
Combined
Financing Receivable, Impaired [Line Items]
Recorded Investment	66,241,000	79,684,000
Unpaid Principal Balance	72,197,000	97,593,000
Related Allowance	3,930,000	5,271,000
Average Recorded Investment	66,362,000	71,037,000
Interest Income Recognized	677,000	291,000
Combined | Commercial | Business loans
Financing Receivable, Impaired [Line Items]
Recorded Investment	15,373,000	12,913,000
Unpaid Principal Balance	21,329,000	21,575,000
Related Allowance	2,983,000	3,124,000
Average Recorded Investment	16,893,000	12,753,000
Interest Income Recognized	0	0
Combined | Construction | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	18,179,000	21,119,000
Unpaid Principal Balance	18,179,000	21,118,000
Related Allowance	14,000	298,000
Average Recorded Investment	18,892,000	21,231,000
Interest Income Recognized	677,000	291,000
Combined | Real estate | Market risk
Financing Receivable, Impaired [Line Items]
Recorded Investment	20,500,000	36,244,000
Unpaid Principal Balance	20,500,000	45,492,000
Related Allowance	535,000	1,131,000
Average Recorded Investment	19,755,000	26,210,000
Interest Income Recognized	0	0
Combined | Real estate | Commercial
Financing Receivable, Impaired [Line Items]
Recorded Investment	8,617,000	6,384,000
Unpaid Principal Balance	8,617,000	6,384,000
Related Allowance	89,000	271,000
Average Recorded Investment	7,122,000	5,841,000
Interest Income Recognized	0	0
Combined | Real estate | Secured by 1-4 family
Financing Receivable, Impaired [Line Items]
Recorded Investment	3,395,000	2,279,000
Unpaid Principal Balance	3,395,000	2,279,000
Related Allowance	275,000	330,000
Average Recorded Investment	3,459,000	2,364,000
Interest Income Recognized	0	0
Combined | Consumer
Financing Receivable, Impaired [Line Items]
Recorded Investment	57,000	313,000
Unpaid Principal Balance	57,000
Related Allowance	16,000	52,000
Average Recorded Investment	59,000	310,000
Interest Income Recognized	0	0
Combined | Leases
Financing Receivable, Impaired [Line Items]
Recorded Investment	120,000	432,000
Unpaid Principal Balance	120,000	432,000
Related Allowance	18,000	65,000
Average Recorded Investment	182,000	2,328,000
Interest Income Recognized	$ 0	$ 0