Non-Qualified Stock Option Transactions (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Shares, Exercised	(2,100)	(1,500)
Outstanding Shares, Cancelled	(32)
Outstanding Weighted Average Exercise Price, Cancelled	$ 37.78
Exercisable Shares at Year End	8,049	8,815
Exercisable Weighted Average Exercise Price at Year-End	$ 30.06	$ 28.58
Exercisable Aggregate Intrinsic Value at Year End	$ 50,365	$ 61,450
Nonqualified Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding Shares, Beginning Balance	10,636
Outstanding Shares, Granted	1,496
Outstanding Shares, Exercised	(1,864)
Outstanding Shares, Forfeited	(88)
Outstanding Shares, Ending Balance	10,148
Outstanding Weighted Average Exercise Price, Beginning Balance	$ 29.07
Outstanding Weighted Average Exercise Price, Granted	$ 36.70
Outstanding Weighted Average Exercise Price, Exercised	$ 22.68
Outstanding Weighted Average Exercise Price, Forfeited	$ 32.52
Outstanding Weighted Average Exercise Price, Ending Balance	$ 31.23
Outstanding Aggregate Intrinsic Value, Balance at Year End	$ 51,402	$ 66,722
Exercisable Shares at Year End	8,049
Exercisable Weighted Average Exercise Price at Year-End	$ 30.06