Shareholders' Equity (Detail) In Millions, except Share data, unless otherwise specified	1 Months Ended		3 Months Ended
	Aug. 31, 2011 USD ($)	Nov. 30, 2010 USD ($)	Mar. 31, 2013 USD ($)	Mar. 31, 2013 CHF	Mar. 31, 2012 USD ($)	Mar. 31, 2012 CHF	Dec. 31, 2012 CHF
Stockholders' Equity Note [Abstract]
Dividends declared per common share			$ 0.49	0.46	$ 0.59	0.53
Common Shares, par value				28.43			28.89
Common Shares in treasury, shares			2,787,156	2,787,156			2,510,878
Stock repurchase program, authorized amount	$ 303	$ 600
Share repurchase authorization remains	197		307
Repurchase of outstanding common shares, shares			1,808,300	1,808,300
Share repurchase amount			$ 154
Increase to dividend approved by shareholders in January					$ 0.12