Summary of Information about Stock-Based Awards Outstanding (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Year	Dec. 31, 2010 Year	Dec. 31, 2009	Dec. 31, 2008
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 32.40	$ 34.35	$ 36.08	$ 39.14
Options Outstanding Number of Shares Outstanding	2,934	2,335	1,745	1,233
Options Outstanding Weighted Average Remaining Contractual Life in Years	4.5	5.1
Options Outstanding Aggregate Intrinsic Value	$ 100	$ 2,262
Options Exercisable Number of Shares Exercisable	1,086	621	331
Options Exercisable Weighted Average Remaining Contractual Life in Years	3.3	4.3
Options Exercisable Aggregate Intrinsic Value	100	655
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	33	34
Options Outstanding Weighted Average Remaining Contractual Life in Years	2.8	3.8
Options Outstanding Aggregate Intrinsic Value	100	500
Options Exercisable Number of Shares Exercisable	33	34
Options Exercisable Weighted Average Remaining Contractual Life in Years	2.8	3.8
Options Exercisable Aggregate Intrinsic Value	100	500
Exercise Price 2
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 20.10	$ 20.10
Options Outstanding Number of Shares Outstanding	8	8
Options Outstanding Weighted Average Remaining Contractual Life in Years	2.8	3.8
Options Outstanding Aggregate Intrinsic Value		71
Options Exercisable Number of Shares Exercisable	8	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	2.8	3.8
Options Exercisable Aggregate Intrinsic Value		71
Exercise Price 3
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 25.74	$ 25.74
Options Outstanding Number of Shares Outstanding	22	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	3.8	4.8
Options Outstanding Aggregate Intrinsic Value		84
Options Exercisable Number of Shares Exercisable	22	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	3.8	4.8
Options Exercisable Aggregate Intrinsic Value		84
Exercise Price 4
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 26.84	$ 26.84
Options Outstanding Number of Shares Outstanding	559	570
Options Outstanding Weighted Average Remaining Contractual Life in Years	4.2	5.2
Options Outstanding Aggregate Intrinsic Value		1,562
Options Exercisable Number of Shares Exercisable	140
Options Exercisable Weighted Average Remaining Contractual Life in Years	4.2
Exercise Price 5
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 28.19	$ 28.19
Options Outstanding Number of Shares Outstanding	30	30
Options Outstanding Weighted Average Remaining Contractual Life in Years	5.8	6.8
Options Outstanding Aggregate Intrinsic Value		42
Options Exercisable Number of Shares Exercisable	30
Options Exercisable Weighted Average Remaining Contractual Life in Years	5.8
Exercise Price 6
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 29.21	$ 29.21
Options Outstanding Number of Shares Outstanding	8	7
Options Outstanding Weighted Average Remaining Contractual Life in Years	5.3	6.7
Options Outstanding Aggregate Intrinsic Value		$ 3
Options Exercisable Number of Shares Exercisable	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	5.3
Exercise Price 7
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 29.95	$ 29.95
Options Outstanding Number of Shares Outstanding	578	592
Options Outstanding Weighted Average Remaining Contractual Life in Years	5.3	6.7
Exercise Price 8
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 34.13	$ 34.13
Options Outstanding Number of Shares Outstanding	227	232
Options Outstanding Weighted Average Remaining Contractual Life in Years	4.3	5.3
Options Exercisable Number of Shares Exercisable	227	232
Options Exercisable Weighted Average Remaining Contractual Life in Years	4.3	5.3
Exercise Price 9
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 37.90	$ 37.90
Options Outstanding Number of Shares Outstanding	15	15
Options Outstanding Weighted Average Remaining Contractual Life in Years	1.8	2.8
Options Exercisable Number of Shares Exercisable	15	15
Options Exercisable Weighted Average Remaining Contractual Life in Years	1.8	2.8
Exercise Price 10
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 38.50	$ 38.50
Options Outstanding Number of Shares Outstanding	22	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	4.8	5.8
Options Exercisable Number of Shares Exercisable	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	4.8
Exercise Price 11
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 38.85	$ 38.85
Options Outstanding Number of Shares Outstanding	8	8
Options Outstanding Weighted Average Remaining Contractual Life in Years	2.2	3.2
Options Exercisable Number of Shares Exercisable	8	8
Options Exercisable Weighted Average Remaining Contractual Life in Years	2.2	3.2
Exercise Price 12
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 42.08	$ 42.08
Options Outstanding Number of Shares Outstanding	343	350
Options Outstanding Weighted Average Remaining Contractual Life in Years	2.3	3.3
Options Exercisable Number of Shares Exercisable	343	173
Options Exercisable Weighted Average Remaining Contractual Life in Years	2.3	3.3
Exercise Price 13
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 45.78	$ 45.78
Options Outstanding Number of Shares Outstanding	417	423
Options Outstanding Weighted Average Remaining Contractual Life in Years	3.3	4.3
Options Exercisable Number of Shares Exercisable	208	106
Options Exercisable Weighted Average Remaining Contractual Life in Years	3.3	4.3
Exercise Price 14
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 52.98	$ 52.98
Options Outstanding Number of Shares Outstanding	22	22
Options Outstanding Weighted Average Remaining Contractual Life in Years	2.8	3.8
Options Exercisable Number of Shares Exercisable	22	22
Options Exercisable Weighted Average Remaining Contractual Life in Years	2.8	3.8
Exercise Price Fifteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 19.10
Options Outstanding Number of Shares Outstanding	30
Options Outstanding Weighted Average Remaining Contractual Life in Years	6.8
Exercise Price Sixteen
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise price	$ 25.65
Options Outstanding Number of Shares Outstanding	612
Options Outstanding Weighted Average Remaining Contractual Life in Years	6.3