Employee Compensation and Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Defined Contribution Plan Description of 401 K Plan
Employee Benefits Disclosure [Line Items]
Maximum percentage of pre-tax income employees are allowed to contribute towards 401(k) plan	75.00%	75.00%	75.00%
Maximum amount of pre-tax income employees are allowed to contribute towards 401(k) plan	$ 16,500	$ 16,500	$ 16,500
Maximum percentage of employer matching contributions towards 401(k) plan	5.00%	5.00%	5.00%
Employee Stock Ownership Plan (ESOP), Plan
Employee Benefits Disclosure [Line Items]
Maximum percentage of employee's eligible pay earned in the fiscal year contributed by the company in cash or common stock towards ESOP	10.00%
ESOP contributions vesting period	5
Employee Home Ownership Plan
Employee Benefits Disclosure [Line Items]
Fixed-rate mortgage loan term, minimum	5 years
Fixed-rate mortgage loan term, maximum	7 years
Amortization period	30 years
Maximum loan amount percentage lesser of purchase price or the appraised value	80.00%
Mortgage loans rate	2.00%
Variable rate	0.25%
Variable rate description	The loan rate shall not be less than the greater of either the five-year Treasury Note plus 25 basis points (for the five year loan) or the average of the five year and 10 year Treasury Note plus 25 basis points (for the seven year loan) or the monthly Applicable Federal Rate for medium-term loans as published by the Internal Revenue Service. The loan rate will be fixed at the time of approval and locked in for 30 days.
Employee Home Ownership Plan | Five year loan
Employee Benefits Disclosure [Line Items]
Note period	5 years
Employee Home Ownership Plan | Seven year loan | Lower Limit
Employee Benefits Disclosure [Line Items]
Note period	5 years
Employee Home Ownership Plan | Seven year loan | Upper Limit
Employee Benefits Disclosure [Line Items]
Note period	10 years
Deferred Compensation Plan
Employee Benefits Disclosure [Line Items]
Maximum percentage of base salary that may be deferred under the DC Plan	25.00%
Maximum percentage of eligible bonus payment that may be deferred under the DC Plan	100.00%
Deferrals under the DC Plan	1,300,000	400,000	600,000
DC Plan investment gains	$ 100,000	$ 400,000	$ 600,000