Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	1 Months Ended				3 Months Ended	12 Months Ended				91 Months Ended	103 Months Ended
	Feb. 27, 2012	Oct. 31, 2011	Oct. 31, 2010	Oct. 29, 2010	Dec. 31, 2010	Dec. 31, 2012	Oct. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Sale of Common Stock, shares	12,000,000
Sale of Common Stock, par value	$ 0.01					$ 0.01		$ 0.01		$ 0.01	$ 0.01
Sale of Common Stock, Price Per Share	$ 30.83
Proceeds from sale of Common Stock						$ 369,584
Underwriting discounts and estimated transaction expenses payable						376
Percentage of stock dividend payable to stockholders as per three-for- two split of common stock				50.00%
Stockholders equity stock split conversion ratio				1.5
Par value of additional shares issued as a result of stock split					394
Repurchase of common stock										39,245,819	39,865,266
Payments for repurchase of common stock						18,597		116,817	166,320	765,443	784,040
Cash dividend per share			$ 0.075			$ 0.370		$ 0.315	$ 0.075
Cash dividend per common share, increase		$ 0.015					$ 0.010
Cash dividends on common stock						44,465		35,566	8,561
Repurchase of common stock, maximum value						1,200,000
Remaining value of common stock authorized under repurchase program						415,960
Common stock, shares authorized but unissued						126,980,506					126,980,506
Outstanding, Number of Shares						1,317,798		1,393,009		1,393,009	1,317,798
Granted, Number of Shares						635,266
Aggregate intrinsic value for options exercisable						9,952					9,952
Aggregate intrinsic value for options outstanding						9,952					9,952
Amount of options that vested						164,314
Total intrinsic value of stock options exercised						6,239		7,597	30,059
Fair value of stock options vested									726
Exercisable options to purchase common stock					1,217,146	484,794		813,767	1,217,146	813,767	484,794
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividend per share		$ 0.075					$ 0.090
Warrant expiration						2014
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividend per share		$ 0.09					$ 0.10
Warrant expiration						2017
Stock Split
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock					2,479
Payments for repurchase of common stock					$ 101
2002 Restricted Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						320,625					320,625
Common stock available for future grants						15,752					15,752
Outstanding, Number of Shares					0	0		0	0	0	0
Granted, Number of Shares						0		0	0
2002 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						8,244,546					8,244,546
Common stock available for future grants						0					0
2002 Stock Option Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of share-based compensation arrangements						10 years
2002 Senior Management Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						9,216,710					9,216,710
Common stock available for future grants						1,500,000					1,500,000
2002 Senior Management Equity Incentive Plan | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price of incentive stock option as a percent of fair market value of Company's common stock						100.00%
2002 Senior Management Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of share-based compensation arrangements						10 years
Exercise price of incentive stock option as a percent of fair market value of Company's common stock						110.00%
2004 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						7,162,500					7,162,500
Common stock available for future grants						1,572,181					1,572,181
Granted, Number of Shares						635,266		500,048	596,463
2004 Equity Incentive Plan | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of share-based compensation arrangements						5 years
2002 Consultant Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock reserved for issuance						675,000					675,000
Common stock available for future grants						205,991					205,991