Schedule of Information Related To Stock Repurchase Programs (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended					12 Months Ended
	Dec. 31, 2012		Dec. 31, 2010 Stock Repurchase Programs Two Thousand Ten		Dec. 31, 2009 Stock Repurchase Programs Two Thousand Ten	Dec. 31, 2011 Stock Repurchase Programs Two Thousand Eleven		Dec. 31, 2012 Stock Repurchase Programs Twenty Twelve
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs	1,384,637					1,384,637
Total price paid for shares purchased as part of publicly announced programs	$ 50,576					$ 50,576
Total number of shares purchased related to stock-based compensation plans	952,894	[1]	301,933	[1]		217,649	[1]	433,312	[1]
Total price paid for shares purchased related to stock-based compensation plans	$ 40,588		$ 11,528			$ 9,906		$ 19,154
Aggregate number of shares purchased	2,337,531		301,933			1,602,286		433,312
Aggregate price paid for shares purchased	$ 91,164		$ 11,528			$ 60,482		$ 19,154
Maximum number of shares that may yet be purchased under the publicly announced program			2,152,339		2,152,339	767,702		767,702

[1] During 2012, there were 432,562 shares repurchased at an average price of $44.28 per share related to income tax withholding obligations in connection with stock-based compensation programs, and 750 shares repurchased at an average of $.01 per share related to restricted shares that were forfeited by former employees pursuant to the terms of our restricted stock purchase plan. During 2011, there were 217,649 shares repurchased at an average price of $45.51 per share related to income tax withholding obligations in connection with stock-based compensation programs. During 2010, there were 293,933 shares repurchased at an average price of $39.22 per share related to income tax withholding obligations in connection with stock-based compensation programs and 8,000 shares repurchased at an average price of $.01 per share related to restricted shares that were forfeited by former employees pursuant to the terms of our restricted stock purchase plan.