Summary of Significant Accounting Policies - Additional Information (Detail)	0 Months Ended
	Nov. 15, 2012
Significant Accounting Policies [Line Items]
Stock split ratio for 100 percent of stock dividend declared	2
Common Stock Class A
Significant Accounting Policies [Line Items]
Stock split ratio for 100 percent of stock dividend declared	2
Common Class B
Significant Accounting Policies [Line Items]
Stock split ratio for 100 percent of stock dividend declared	2