Restricted Stock Units - Activity (Detail) (Restricted Stock Units, USD $)	12 Months Ended				1 Months Ended	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011	Dec. 31, 2010	Jan. 31, 2013 Long Term Incentive Plans	Dec. 31, 2012 Settled in Cash	Dec. 31, 2011 Settled in Cash
Units
Outstanding, beginning of period	2,718,950		2,813,567
Granted	1,395,346	[1]	1,070,762		1,011,665
Delivered	(654,612)		(654,000)
Forfeited	(199,098)	[2]	(511,379)			0	(30,144)
Outstanding, end of period	3,260,586		2,718,950	2,813,567
Grant Date Weighted Average Fair Value
Outstanding, beginning of period	$ 71.17		$ 70.55
Granted	$ 47.72		$ 72.75	$ 78.19
Delivered	$ 70.96		$ 65.18
Forfeited	$ 58.94		$ 74.21
Outstanding, end of period	$ 62.71		$ 71.17	$ 70.55

[1] Excludes 1,011,665 stock units granted to employees subsequent to December 31, 2012 as part of the long term incentive awards program.

[2] Included in the 2011 forfeited balance are 30,144 restricted stock units settled in cash as described above. There were no restricted stock units settled in cash in 2012.