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				12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012		Dec. 31, 2012
Total impaired loans [Abstract]
Recorded balance	$ 66,454		$ 59,966		$ 62,498
Unpaid Contractual Principal Balance	72,539		65,721		68,596
Specific Allowance	3,425		4,530		3,248
Average investment in impaired loans	66,335		60,277		62,624
Interest Income Recognized	532	[1]	369	[1]	1,880	[1]
Commercial Construction [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	5,155		4,594		3,692
Unpaid Contractual Principal Balance	5,609		4,595		4,146
Specific Allowance	0		0		0
Average Investment in Impaired Loans	5,225		4,683		4,249
Interest Income Recognized	74	[1]	18	[1]	97	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	6,073		5,912		5,703
Unpaid Contractual Principal Balance	7,303		6,764		6,933
Specific Allowance	1,911		2,180		1,820
Average Investment in Impaired Loans	6,075		5,809		6,585
Interest income recognized	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	11,228		10,506		9,395
Unpaid Contractual Principal Balance	12,912		11,359		11,079
Specific Allowance	1,911		2,180		1,820
Average investment in impaired loans	11,300		10,492		10,834
Interest Income Recognized	74	[1]	18	[1]	97	[1]
Commercial Secured by Real Estate [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	33,765		36,312		35,046
Unpaid Contractual Principal Balance	34,586		37,778		35,818
Specific Allowance	0		0		0
Average Investment in Impaired Loans	33,908		36,506		35,542
Interest Income Recognized	297	[1]	332	[1]	1,337	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	4,158		3,382		3,067
Unpaid Contractual Principal Balance	4,276		3,508		3,189
Specific Allowance	1,192		1,246		1,090
Average Investment in Impaired Loans	4,166		3,385		3,243
Interest income recognized	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	37,923		39,694		38,113
Unpaid Contractual Principal Balance	38,862		41,286		39,007
Specific Allowance	1,192		1,246		1,090
Average investment in impaired loans	38,074		39,891		38,785
Interest Income Recognized	297	[1]	332		1,337	[1]
Commercial Other [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	15,779		6,696		13,285
Unpaid Contractual Principal Balance	17,920		7,406		15,484
Specific Allowance	0		0		0
Average Investment in Impaired Loans	15,435		6,785		11,083
Interest Income Recognized	154	[1]	16	[1]	416	[1]
Loans with a specific valuation allowance [Abstract]
Recorded Balance	867		2,791		1,010
Unpaid Contractual Principal Balance	2,188		5,391		2,331
Specific Allowance	322		1,104		338
Average Investment in Impaired Loans	868		2,829		1,441
Interest income recognized	0	[1]	0	[1]	0	[1]
Total impaired loans [Abstract]
Recorded balance	16,646		9,487		14,295
Unpaid Contractual Principal Balance	20,108		12,797		17,815
Specific Allowance	322		1,104		338
Average investment in impaired loans	16,303		9,614		12,524
Interest Income Recognized	154	[1]	16		416	[1]
Real Estate Mortgage [Member]
Loans without a specific valuation allowance [Abstract]
Recorded Balance	657		279		695
Unpaid Contractual Principal Balance	657		279		695
Specific Allowance	0		0		0
Average Investment in Impaired Loans	658		280		481
Interest Income Recognized	7	[1]	3	[1]	30	[1]
Total impaired loans [Abstract]
Recorded balance	657		279		695
Unpaid Contractual Principal Balance	657		279		695
Specific Allowance	0		0		0
Average investment in impaired loans	658		280		481
Interest Income Recognized	$ 7	[1]	$ 3	[1]	$ 30	[1]

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