Loans, Impaired Loans, Average Investments in Impaired Loans, and Interest Income Recognized on Impaired Loans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended				12 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Total impaired loans [Abstract]
Recorded balance	$ 63,418		$ 64,448		$ 63,418		$ 64,448		$ 62,498
Unpaid Contractual Principal Balance	69,876		70,370		69,876		70,370		68,596
Specific Allowance	3,839		3,329		3,839		3,329		3,248
Average investment in impaired loans	63,648		64,722		64,993		62,500		62,624
Interest Income Recognized	457	[1]	441	[1]	989	[1]	810	[1]	1,880	[1]
Commercial Construction [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	5,921		4,554		5,921		4,554		3,692
Unpaid Contractual Principal Balance	6,498		4,554		6,498		4,554		4,146
Specific Allowance	0		0		0		0		0
Average Investment in Impaired Loans	6,043		4,499		5,634		4,591		4,249
Interest Income Recognized	53	[1]	40	[1]	127	[1]	58	[1]	97	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	4,655		7,561		4,655		7,561		5,703
Unpaid Contractual Principal Balance	5,511		8,414		5,511		8,414		6,933
Specific Allowance	1,890		1,823		1,890		1,823		1,820
Average Investment in Impaired Loans	4,656		7,479		5,366		6,644		6,585
Interest income recognized	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	10,576		12,115		10,576		12,115		9,395
Unpaid Contractual Principal Balance	12,009		12,968		12,009		12,968		11,079
Specific Allowance	1,890		1,823		1,890		1,823		1,820
Average investment in impaired loans	10,699		11,978		11,000		11,235		10,834
Interest Income Recognized	53	[1]	40	[1]	127	[1]	58	[1]	97	[1]
Commercial Secured by Real Estate [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	29,232		35,835		29,232		35,835		35,046
Unpaid Contractual Principal Balance	30,155		36,307		30,155		36,307		35,818
Specific Allowance	0		0		0		0		0
Average Investment in Impaired Loans	29,422		35,964		31,665		36,235		35,542
Interest Income Recognized	236	[1]	353	[1]	533	[1]	685	[1]	1,337	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	6,194		3,057		6,194		3,057		3,067
Unpaid Contractual Principal Balance	6,448		4,196		6,448		4,196		3,189
Specific Allowance	1,866		1,084		1,866		1,084		1,090
Average Investment in Impaired Loans	6,298		3,059		5,232		3,222		3,243
Interest income recognized	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	35,426		38,892		35,426		38,892		38,113
Unpaid Contractual Principal Balance	36,603		40,503		36,603		40,503		39,007
Specific Allowance	1,866		1,084		1,866		1,084		1,090
Average investment in impaired loans	35,720		39,023		36,897		39,457		38,785
Interest Income Recognized	236	[1]	353	[1]	533	[1]	685	[1]	1,337	[1]
Commercial Other [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	16,036		12,253		16,036		12,253		13,285
Unpaid Contractual Principal Balance	19,760		14,382		19,760		14,382		15,484
Specific Allowance	0		0		0		0		0
Average Investment in Impaired Loans	15,825		12,504		15,630		9,645		11,083
Interest Income Recognized	151	[1]	43	[1]	305	[1]	59	[1]	416	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	353		911		353		911		1,010
Unpaid Contractual Principal Balance	477		2,239		477		2,239		2,331
Specific Allowance	83		422		83		422		338
Average Investment in Impaired Loans	379		939		624		1,884		1,441
Interest income recognized	0	[1]	0	[1]	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	16,389		13,164		16,389		13,164		14,295
Unpaid Contractual Principal Balance	20,237		16,621		20,237		16,621		17,815
Specific Allowance	83		422		83		422		338
Average investment in impaired loans	16,204		13,443		16,254		11,529		12,524
Interest Income Recognized	151	[1]	43	[1]	305	[1]	59	[1]	416	[1]
Real Estate Mortgage [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	1,027		277		1,027		277		695
Unpaid Contractual Principal Balance	1,027		278		1,027		278		695
Specific Allowance	0		0		0		0		0
Average Investment in Impaired Loans	1,025		278		842		279		481
Interest Income Recognized	17	[1]	5	[1]	24	[1]	8	[1]	30	[1]
Total impaired loans [Abstract]
Recorded balance	1,027		277		1,027		277		695
Unpaid Contractual Principal Balance	1,027		278		1,027		278		695
Specific Allowance	0		0		0		0		0
Average investment in impaired loans	1,025		278		842		279		481
Interest Income Recognized	$ 17	[1]	$ 5	[1]	$ 24	[1]	$ 8	[1]	$ 30	[1]

[1] Cash basis interest is substantially the same as interest income recognized.