Capital Stock - Capital Stock (Detail)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Equity [Line Items]
Beginning balance	162,514,098	161,131,547
Stock options/SARs exercised	206,949	926,425
Restricted stock granted	106,969	354,674
Restricted stock units vested	112,751	57,824
Treasury shares issued	26,026	43,628
Ending balance	162,966,793	162,514,098