Common Stock and Class B Common Stock - Additional Information (Detail)	Dec. 31, 2012	Dec. 31, 2011
Components Of Common Stock [Line Items]
Number of directors stockholders entitle to elect	9
Subsidiary
Components Of Common Stock [Line Items]
Number of treasury shares held	145,820	145,820
If 1,050,000 or more shares of Class B Common Stock are outstanding
Components Of Common Stock [Line Items]
Number of directors stockholders entitle to elect	4
If between 600,000 and 1,050,000 shares are outstanding
Components Of Common Stock [Line Items]
Number of directors stockholders entitle to elect	3
If less than 600,000 shares of Class B Common Stock are outstanding
Components Of Common Stock [Line Items]
Number of directors stockholders entitle to elect	0