Shareholders' Equity (Detail) In Millions, except Share data, unless otherwise specified	1 Months Ended			3 Months Ended				6 Months Ended
	Jan. 31, 2012 USD ($)	Aug. 31, 2011 USD ($)	Nov. 30, 2010 USD ($)	Jun. 30, 2012 USD ($)	Jun. 30, 2012 CHF	Jun. 30, 2011 USD ($)	Jun. 30, 2011 CHF	Jun. 30, 2012 USD ($)	Jun. 30, 2012 CHF	Jun. 30, 2011 USD ($)	Jun. 30, 2011 CHF	Dec. 31, 2011 CHF
Stockholders' Equity [Line Items]
Dividends declared per common share				$ 0.49	0.48	$ 0.35	0.29	$ 1.08	1.01	$ 0.68	0.59
Par value reduction per common share					0.48		0.30		0.48		0.30
Common Shares, par value					29.79				29.79			30.27
Common Share dividend increase approved by shareholders in January 2012								$ 0.12
Common Shares in treasury, shares				3,771,527	3,771,527			3,771,527	3,771,527			5,905,136
Stock repurchase program, authorized amount		$ 303	$ 600
Share repurchase authorization remains		197						461
Repurchase of outstanding common shares, shares	100,000
Transaction cost	$ 7