Fair Value (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Fair Value [Abstract]
Discount percentage applied to real estate appraised values	15.00%
Discount percentage applied to lot development appraised values	6.00%
Book value of impaired loans	$ 179,424,000	$ 238,959,000	$ 187,135,000
Partial charge-offs on impaired loans	108,300,000		103,800,000
Valuation allowance of impaired loans	9,505,000		15,935,000
Book value of impaired loans carried at fair value	92,800,000		87,800,000
Remaining amount of impaired loans carried at cost	86,500,000		83,400,000
MSR recorded at lower of cost or fair value	8,975,000	10,365,000	9,301,000	10,488,000
Mortgage servicing rights	7,138,000		5,815,000
Valuation allowance of MSR	1,021,000	680,000	1,021,000	748,000
MSRs recorded at cost	1,900,000
Impaired loans carried at fair value	83,324,000		87,813,000
Estimated fair value of OREO, less estimated selling costs	41,965,000		42,272,000
OREO devaluations	$ 1,359,000	$ 2,535,000