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Stockholders' Equity - Additional Information (Detail) - USD ($) | 3 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Dec. 31, 2017 | Sep. 30, 2017 | Jun. 30, 2017 | Mar. 31, 2017 | Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2012 | Oct. 31, 2016 | Jul. 31, 2015 | Feb. 28, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Preferred stock, shares authorized | 500,000 |  |  |  | 500,000 |  |  |  |  |  |  |  | 500,000 | 500,000 |  |  |  |  |
Preferred stock, par value | $ 0.01 |  |  |  | $ 0.01 |  |  |  |  |  |  |  | $ 0.01 | $ 0.01 |  |  |  |  |
Authorized to purchase of common stock under the stock repurchase program | $ 485,000,000 |  |  |  |  |  |  |  |  |  |  |  | $ 485,000,000 |  |  |  | $ 25,000,000 | $ 25,000,000 | $ 25,000,000
Cumulative repurchase of common stock | 16,100,000 |  |  |  |  |  |  |  |  |  |  |  | 16,100,000 |  |  |  |  |  |
Aggregate cost of repurchase of common stock |  |  |  |  |  |  |  |  |  |  |  |  | $ 464,900,000 |  |  |  |  |  |
Dividend declared and paid per share | $ 0.19 | $ 0.19 | $ 0.19 | $ 0.19 | $ 0.18 | $ 0.18 | $ 0.18 | $ 0.18 | $ 0.17 | $ 0.17 | $ 0.17 | $ 0.17 |  |  |  |  |  |  |
Dividend declared per share |  |  |  |  |  |  |  |  |  |  |  |  | $ 0.76 | $ 0.72 | $ 0.68 |  |  |  |
Aggregate dividend declared for the year |  |  |  |  |  |  |  |  |  |  |  |  | $ 13,600,000 | $ 13,000,000 | $ 12,200,000 |  |  |  |
Option Outstanding and vested | 937,000 |  |  |  | 1,540,000 |  |  |  |  |  |  |  | 937,000 | 1,540,000 |  |  |  |  |
Employee Stock Purchase Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future awards granted or issued under plans | 100,000 |  |  |  |  |  |  |  |  |  |  |  | 100,000 |  |  |  |  |  |
Shares authorized | 700,000 |  |  |  |  |  |  |  |  |  |  |  | 700,000 |  |  |  |  |  |
Hours of work per week |  |  |  |  |  |  |  |  |  |  |  |  | 20 hours |  |  |  |  |  |
Duration of purchase periods under employee stock purchase plan |  |  |  |  |  |  |  |  |  |  |  |  | 6 months |  |  |  |  |  |
Holding period of stocks acquired under employee stock purchase plan |  |  |  |  |  |  |  |  |  |  |  |  | 1 year |  |  |  |  |  |
Value used to derive maximum number of shares per participant for employee stock purchase |  |  |  |  |  |  |  |  |  |  |  |  | $ 12,500 |  |  |  |  |  |
Employee maximum elected percentage reduction of compensation to purchase shares | 10.00% |  |  |  |  |  |  |  |  |  |  |  | 10.00% |  |  |  |  |  |
Exercise price rate of fair value |  |  |  |  |  |  |  |  |  |  |  |  | 85.00% |  |  |  |  |  |
Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Weighted average grant date fair value for RSUs granted |  |  |  |  |  |  |  |  |  |  |  |  | $ 39.73 | $ 37.87 | $ 31.50 |  |  |  |
Number of shares received per restricted stock unit on lapse of restrictions and vesting condition met |  |  |  |  |  |  |  |  |  |  |  |  | 1 |  |  |  |  |  |
Value of RSUs vested and converted to common stock |  |  |  |  |  |  |  |  |  |  |  |  | $ 8,700,000 | $ 6,600,000 | $ 4,600,000 |  |  |  |
Stock Options [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Intrinsic value of options exercised |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,500,000 | $ 3,700,000 | $ 400,000 |  |  |  |
1996 Equity Plan [Member] | Equity Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future awards granted or issued under plans | 0 |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |
2006 Director Plan [Member] | Equity Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future awards granted or issued under plans | 0 |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |
Shares authorized | 450,000,000 |  |  |  |  |  |  |  |  |  |  |  | 450,000,000 |  |  |  |  |  |
Shares returned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 80,000 |  |  |
Option Outstanding and vested | 100,000 |  |  |  |  |  |  |  |  |  |  |  | 100,000 |  |  |  |  |  |
1996 Director [Member] | Equity Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future awards granted or issued under plans | 0 |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |
Equity Incentive Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Equity incentive plan extended term |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |
Equity incentive plan expiration |  |  |  |  |  |  |  |  |  |  |  |  | 2026-05 |  |  |  |  |  |
Increase in number of shares issuable under plan |  |  |  |  |  |  |  |  |  |  |  |  | 2,000,000 |  |  |  |  |  |
Equity Incentive Plan [Member] | Equity Plan [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Future awards granted or issued under plans | 2,600,000 |  |  |  |  |  |  |  |  |  |  |  | 2,600,000 |  |  |  |  |  |
Shares authorized |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 6,350,000 |  |  |
Shares returned |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 713,275 |  |  |
Option expiration period |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |  |  |  |  |  |
Equity Incentive Plan [Member] | Equity Plan [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Options vested period |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |
Equity Incentive Plan [Member] | Equity Plan [Member] | Non-Employee Directors [Member] | Restricted Stock Units (RSUs) [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Options vested period |  |  |  |  |  |  |  |  |  |  |  |  | 1 year |  |  |  |  |  |

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