Organization - Additional Information (Detail)	9 Months Ended				67 Months Ended		9 Months Ended			9 Months Ended
	Sep. 30, 2014 Office Segment	Sep. 30, 2014 Class A common stock [Member]	Sep. 30, 2014 Class A common stock [Member] Stock Repurchase Program One [Member]	Sep. 30, 2013 Class A common stock [Member] Stock Repurchase Program One [Member]	Sep. 30, 2014 Class A common stock [Member] Stock Repurchase Program One [Member]	Feb. 23, 2009 Class A common stock [Member] Stock Repurchase Program One [Member]	Sep. 30, 2014 Class A common stock [Member] Stock Repurchase Program Two [Member]	Sep. 30, 2013 Class A common stock [Member] Stock Repurchase Program Two [Member]	Jul. 18, 2013 Class A common stock [Member] Stock Repurchase Program Two [Member]	Sep. 30, 2014 Class B common stock [Member]
Business Acquisition [Line Items]
Operations Commenced Date	Aug. 26, 1986
Outstanding stock percentage	48.20%
Stock ownership percentage owned by third party	51.80%
Number of banking offices	14
Number of operating segments	4
Stock ownership percentage held by major shareholder		36.00%								76.00%
Voting power percentage of outstanding common stock	65.00%
Percentage of share in results of pooled business	80.00%
Percentage of share in results of pooled business owned by third party	20.00%
Number of common stock shares purchased						300,000			500,000
Common stock shares purchased			846	4,240	296,778		0	0