Summary of Significant Accounting Policies (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013 Segment Trust	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Summary of Significant Accounting Policies (Textual) [Abstract]
Allowance for loan losses	$ 39,867,000	$ 42,648,000	$ 45,452,000	$ 45,914,000
Method used to estimate net sale proceeds	Greater of fifteen percent or actual estimated selling costs
Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Number of subsidiary business trust	2
Number of business segments	1
Loans contractual past due	90 days
Recognized OTTI losses	0	0
TDR loans payment period in non accrual status	6 months
Tri countries bank [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Number of traditional operating branches	41
Number of in-store operating branches	25
Impaired real estate collateral dependent loans [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Allowance for loan losses	$ 494,000
Furniture and equipment [Member] | Maximum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Estimated useful lives of the related assets or lease terms	10 years
Furniture and equipment [Member] | Minimum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Estimated useful lives of the related assets or lease terms	3 years
Land improvements and buildings [Member] | Maximum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Estimated useful lives of the related assets or lease terms	40 years
Land improvements and buildings [Member] | Minimum [Member]
Summary of Significant Accounting Policies (Textual) [Abstract]
Estimated useful lives of the related assets or lease terms	15 years