Operating Segments (Narrative) (Details)	12 Months Ended
Dec. 31, 2012 segment state
Operating Segments [Abstract]
Number of principal segments	6
Number of operating units in the secondary market	3
Out of market segment description	Loans included in the Out of Market segment are portfolio loans attributable to twenty-six states other than Oklahoma, Texas, or Kansas and primarily consist of healthcare and commercial real estate credits. These out of state loans are administered by offices in Oklahoma, Texas, or Kansas.
Number of states to which loans are attributed	26

Number of operating segments. An operating segment is a component of an enterprise: (a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same enterprise), (b) whose operating results are regularly reviewed by the enterprise's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and (c) for which discrete financial information is available. An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

No definition available.

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