Summary of Information about Stock-Based Awards Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 30.09	$ 32.40	$ 34.35	$ 36.08
Options Outstanding Number of Shares Outstanding	3,563	2,934	2,335	1,745
Options Outstanding Weighted Average Remaining Contractual Life in Years	4 years	4 years 6 months
Options Outstanding Aggregate Intrinsic Value	$ 173	$ 100
Options Exercisable Number of Shares Exercisable	1,592	1,086
Options Exercisable Weighted Average Remaining Contractual Life in Years	2 years 7 months 6 days	3 years 3 months 18 days
Options Exercisable Aggregate Intrinsic Value	141	100
Exercise Price 1
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 15.00	$ 15.00
Options Outstanding Number of Shares Outstanding	32	33
Options Outstanding Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days	2 years 9 months 18 days
Options Outstanding Aggregate Intrinsic Value	136	100
Options Exercisable Number of Shares Exercisable	32	33
Options Exercisable Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days	2 years 9 months 18 days
Options Exercisable Aggregate Intrinsic Value	136	100
Exercise Price 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 18.56	$ 19.10
Options Outstanding Number of Shares Outstanding	45	30
Options Outstanding Weighted Average Remaining Contractual Life in Years	6 years 9 months 18 days	6 years 9 months 18 days
Options Outstanding Aggregate Intrinsic Value	32
Exercise Price 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 19.10	$ 20.10
Options Outstanding Number of Shares Outstanding	30	8
Options Outstanding Weighted Average Remaining Contractual Life in Years	5 years 9 months 18 days	2 years 9 months 18 days
Options Outstanding Aggregate Intrinsic Value	5
Options Exercisable Number of Shares Exercisable	30	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	5 years 9 months 18 days	2 years 9 months 18 days
Options Exercisable Aggregate Intrinsic Value	$ 5
Exercise Price 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 19.69	$ 25.65
Options Outstanding Number of Shares Outstanding	30	612
Options Outstanding Weighted Average Remaining Contractual Life in Years	6 years 7 months 6 days	6 years 3 months 18 days
Exercise Price 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 20.10	$ 25.74
Options Outstanding Number of Shares Outstanding	8	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days	3 years 9 months 18 days
Options Exercisable Number of Shares Exercisable	8	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days	3 years 9 months 18 days
Exercise Price 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 20.13	$ 26.84
Options Outstanding Number of Shares Outstanding	594	559
Options Outstanding Weighted Average Remaining Contractual Life in Years	6 years 3 months 18 days	4 years 2 months 12 days
Options Exercisable Number of Shares Exercisable		140
Options Exercisable Weighted Average Remaining Contractual Life in Years		4 years 2 months 12 days
Exercise Price 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 25.65	$ 28.19
Options Outstanding Number of Shares Outstanding	598	30
Options Outstanding Weighted Average Remaining Contractual Life in Years	5 years 3 months 18 days	5 years 9 months 18 days
Options Exercisable Number of Shares Exercisable		30
Options Exercisable Weighted Average Remaining Contractual Life in Years		5 years 9 months 18 days
Exercise Price 8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 25.74	$ 29.21
Options Outstanding Number of Shares Outstanding	23	8
Options Outstanding Weighted Average Remaining Contractual Life in Years	2 years 9 months 18 days	5 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	23	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	2 years 9 months 18 days	5 years 3 months 18 days
Exercise Price 9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 26.84	$ 29.95
Options Outstanding Number of Shares Outstanding	552	578
Options Outstanding Weighted Average Remaining Contractual Life in Years	3 years 2 months 12 days	5 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	276
Options Exercisable Weighted Average Remaining Contractual Life in Years	3 years 2 months 12 days
Exercise Price 10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 28.19	$ 34.13
Options Outstanding Number of Shares Outstanding	30	227
Options Outstanding Weighted Average Remaining Contractual Life in Years	4 years 9 months 18 days	4 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	30	227
Options Exercisable Weighted Average Remaining Contractual Life in Years	4 years 9 months 18 days	4 years 3 months 18 days
Exercise Price 11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 29.21	$ 37.90
Options Outstanding Number of Shares Outstanding	8	15
Options Outstanding Weighted Average Remaining Contractual Life in Years	4 years 3 months 18 days	1 year 9 months 18 days
Options Exercisable Number of Shares Exercisable	8	15
Options Exercisable Weighted Average Remaining Contractual Life in Years	4 years 3 months 18 days	1 year 9 months 18 days
Exercise Price 12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 29.95	$ 38.50
Options Outstanding Number of Shares Outstanding	567	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	4 years 3 months 18 days	4 years 9 months 18 days
Options Exercisable Number of Shares Exercisable	139	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	4 years 3 months 18 days	4 years 9 months 18 days
Exercise Price 13
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 34.13	$ 38.85
Options Outstanding Number of Shares Outstanding	225	8
Options Outstanding Weighted Average Remaining Contractual Life in Years	3 years 3 months 18 days	2 years 2 months 12 days
Options Exercisable Number of Shares Exercisable	225	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	3 years 3 months 18 days	2 years 2 months 12 days
Exercise Price 14
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 37.90	$ 42.08
Options Outstanding Number of Shares Outstanding	15	343
Options Outstanding Weighted Average Remaining Contractual Life in Years	9 months 18 days	2 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	15	343
Options Exercisable Weighted Average Remaining Contractual Life in Years	9 months 18 days	2 years 3 months 18 days
Exercise Price Fifteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 38.50	$ 45.78
Options Outstanding Number of Shares Outstanding	23	417
Options Outstanding Weighted Average Remaining Contractual Life in Years	3 years 9 months 18 days	3 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	23	208
Options Exercisable Weighted Average Remaining Contractual Life in Years	3 years 9 months 18 days	3 years 3 months 18 days
Exercise Price Sixteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 38.85	$ 52.98
Options Outstanding Number of Shares Outstanding	8	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	1 year 2 months 12 days	2 years 9 months 18 days
Options Exercisable Number of Shares Exercisable	8	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	1 year 2 months 12 days	2 years 9 months 18 days
Exercise Price Seventeen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 42.08
Options Outstanding Number of Shares Outstanding	340
Options Outstanding Weighted Average Remaining Contractual Life in Years	1 year 3 months 18 days
Options Exercisable Number of Shares Exercisable	340
Options Exercisable Weighted Average Remaining Contractual Life in Years	1 year 3 months 18 days
Exercise Price Eighteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 45.78
Options Outstanding Number of Shares Outstanding	412
Options Outstanding Weighted Average Remaining Contractual Life in Years	2 years 3 months 18 days
Options Exercisable Number of Shares Exercisable	412
Options Exercisable Weighted Average Remaining Contractual Life in Years	2 years 3 months 18 days
Exercise Price Nineteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 52.98
Options Outstanding Number of Shares Outstanding	23
Options Outstanding Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days
Options Exercisable Number of Shares Exercisable	23
Options Exercisable Weighted Average Remaining Contractual Life in Years	1 year 9 months 18 days