Annual report pursuant to Section 13 and 15(d)

Subsequent Events - Additional Information (Detail)

v2.4.0.6
Subsequent Events - Additional Information (Detail)
 3 Months Ended 1 Months Ended
Dec. 31, 2012
Sep. 30, 2012
Jun. 30, 2012
Mar. 31, 2012
Feb. 28, 2013
Subsequent Event
Feb. 28, 2013
Subsequent Event
March Stock Dividend
Subsequent Event [Line Items]            
Stock dividend policy adopted         2.00% 2.00%
Stock dividends declared 0.50% 0.50% 0.50% 0.50%   0.50%
Dividends declared, date of record Dec. 14, 2012 Sep. 14, 2012 Jun. 08, 2012 Mar. 15, 2012   Mar. 15, 2013