Organization and Principles of Consolidation - Additional Information (Detail) - 6 months ended Jun. 30, 2015	Trust Office
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Ownership interest owned finance subsidiary business trusts	100.00%
Number of finance subsidiary trusts | Trust	8
Number of offices	164
Arkansas [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	80
Georgia [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	28
North Carolina [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	16
Texas [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	21
Florida [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	11
Alabama [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	3
South Carolina [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	2
New York [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	2
California [Member]
Organization Consolidation And Presentation Of Financial Statements [Line Items]
Number of offices	1