Stock Compensation Plans - SSAR's and Stock Option Activity (Detail) (USD $)	12 Months Ended
	Dec. 31, 2010	Dec. 31, 2012 SSAR's and Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Balance at December 31, 2011, Shares Subject to SSAR's/Options		1,090,000
Granted, Shares Subject to SSAR's/Options		54,000
Exercised, Shares Subject to SSAR's/Options	(779,317)	(443,000)
Cancelled, Shares Subject to SSAR's/Options		(95,000)
Balance at December 31, 2012, Shares Subject to SSAR's/Options		606,000
Balance at December 31, 2011, Weighted Average Exercise Price		$ 39.16
Granted, Weighted Average Exercise Price		$ 60.39
Exercised, Weighted Average Exercise Price		$ 34.87
Cancelled, Weighted Average Exercise Price		$ 36.75
Balance at December 31, 2012, Weighted Average Exercise Price		$ 44.68
Balance at December 31, 2011, SSAR's/Options Exercisable		627,000
Balance at December 31, 2012, SSAR's/Options Exercisable		320,000