Capital Stock - Additional Information (Detail)	Jun. 30, 2013	Dec. 31, 2012
Equity [Line Items]
Authorized capital stock	485,000,000	485,000,000
Common stock, shares authorized	475,000,000	475,000,000
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding