Traditional Banking Credit Quality Ratios (Detail)	Sep. 30, 2012	Dec. 31, 2011
Credit Quality Ratio [Line Items]
Non-performing loans to total loans	0.80%	1.02%
Non-performing assets to total loans (including OREO)	1.73%	1.49%
Non-performing assets to total assets	1.34%	1.00%
Traditional Banking
Credit Quality Ratio [Line Items]
Non-performing loans to total loans	0.80%	1.02%
Non-performing assets to total loans (including OREO)	1.73%	1.49%
Non-performing assets to total assets	1.34%	1.10%