Common Stock and Class B Common Stock - Additional Information (Detail) $ in Millions	Jan. 26, 2016 USD ($) shares	Dec. 31, 2015 director shares	Dec. 31, 2014 shares
Class of Stock [Line Items]
Number of directors stockholders entitle to elect		9
Subsidiaries
Class of Stock [Line Items]
Number of treasury shares held | shares		145,820	145,820
Conversion, Class B Common Stock to Common Stock | Subsequent Event
Conversion of Stock [Line Items]
Conversion of Stock, additional cash issued to Class B Common Stock holders | $	$ 12.0
Conversion, Class B Common Stock to Common Stock | Subsequent Event | Class B Common Stock
Conversion of Stock [Line Items]
Conversion of stock, number of shares converted | shares	1,050,012
Conversion, Class B Common Stock to Common Stock | Subsequent Event | Common Stock
Conversion of Stock [Line Items]
Conversion of stock, number of shares issued | shares	1,050,012
If 1,050,000 or more shares of Class B Common Stock are outstanding
Class of Stock [Line Items]
Number of directors stockholders entitle to elect		4
If between 600,000 and 1,050,000 shares of Class B Common Stock are outstanding
Class of Stock [Line Items]
Number of directors stockholders entitle to elect		3
If less than 600,000 shares of Class B Common Stock are outstanding
Class of Stock [Line Items]
Number of directors stockholders entitle to elect		0