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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Stockholders' Equity - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended												12 Months Ended
	May 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	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, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2012	Feb. 28, 2018
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		$ 535,000,000												$ 535,000,000				$ 50,000,000
Cumulative repurchase of common stock		16,300,000												16,300,000
Aggregate cost of repurchase of common stock														$ 474,900,000
Dividend declared and paid per share		$ 0.20	$ 0.20	$ 0.20	$ 0.20	$ 0.19	$ 0.19	$ 0.19	$ 0.19	$ 0.18	$ 0.18	$ 0.18	$ 0.18
Dividend declared per share														$ 0.80	$ 0.76	$ 0.72
Aggregate dividend declared for the year														$ 14,500,000	$ 13,600,000	$ 13,000,000
Option Outstanding and vested		583,000				937,000								583,000	937,000
Common stock, par value		$ 0.01				$ 0.01								$ 0.01	$ 0.01
Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Future awards granted or issued under plans	500,000
Increase in number of shares issuable under plan	400,000
Shares authorized	1,100,000
Common stock, par value	$ 0.01
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%
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														$ 43.71	$ 39.73	$ 37.87
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														$ 9,100,000	$ 8,700,000	$ 6,600,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised														$ 3,300,000	$ 4,500,000	$ 3,700,000
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		2,500,000												2,500,000
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
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												450,000
Shares returned																	80,000,000
Option Outstanding and vested		36,000												36,000
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