Common Stock - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Nov. 30, 2017	Feb. 29, 2016	Jul. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase programs authorized to purchase, value	$ 1,200,000,000	$ 800,000,000		$ 400,000,000	$ 400,000,000	$ 400,000,000
Stock repurchased, value	356,413,000	346,890,000	$ 224,260,000
Compensation cost recognized	$ 56,738,000	48,109,000	39,971,000
Forfeitures utilization term	5 years
Total in-the-money value of all stock options exercised during the year	$ 85,500,000	149,400,000	154,100,000
Number of shares granted	3,061,725
Stock issued during period, net of cancellations	1,500,000
Class B
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, value	$ 33,000	30,000	18,000
Shares reserved	2,800,000
Issuance upon conversion of shares	26,069,031
ASU 2016-09
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
New accounting adoption impact on income taxes and net income	$ 22,100,000
Excess tax benefit from stock-based compensation		45,200,000	47,400,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognized, pre-tax charge	54,300,000	45,800,000	38,000,000
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost recognized, after-tax	2,500,000	$ 2,300,000	$ 2,000,000
Unrecognized compensation cost	$ 98,200,000
Unrecognized compensation cost vesting period	2 years 7 months 6 days
Unvested Stock option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost	$ 98,200,000
Unrecognized compensation cost vesting period	2 years 7 months 6 days
Income Tax Withholding Obligations
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, shares	305,278	468,228	493,296
Stock repurchased, value	$ 34,200,000	$ 57,000,000	$ 58,000,000
Forfeited Restricted Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, shares		2,500
Stock Repurchase Programs Twenty Seventeen
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase programs authorized to purchase, value	$ 400,000,000
Stock repurchased, shares	2,960,843
Stock repurchased, value	$ 322,231,000
Stock Repurchase Programs Twenty Seventeen | Stock Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, shares	6,799,642
Stock repurchased, value	$ 778,390,000
Stock Repurchase Programs Twenty Sixteen
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase programs authorized to purchase, value		$ 400,000,000
Stock Repurchase Programs Twenty Sixteen | Stock Repurchase Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, shares		2,512,592
Stock repurchased, value		$ 289,937,000
Stock Repurchase Programs Twenty Fifteen
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchased, shares			1,326,207
Stock repurchased, value			$ 166,222,000
Stock Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of option granted, number of shares	2,900,000	2,700,000	2,700,000
Weighted-average grant date fair value of option granted, per share	$ 27.05	$ 23.80	$ 21.37
Common Stock remain available for issuance	7,800,000
Stock Incentive Plan | Class B
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved	35,600,000
Stock Incentive Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options are exercisable, in period	4 years
2005 Employees' Restricted Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock remain available for issuance	1,300,000
Number of shares granted	86,693	75,792	68,213
2005 Employees' Restricted Stock Purchase Plan | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock issued under employee stock purchase plan	23,557	14,146	17,789
2005 Employees' Restricted Stock Purchase Plan | Restricted Stock | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares vesting period	5 years	5 years	5 years
Special Dividend
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Dividends declared and paid, per share	$ 0.40	$ 0.40	$ 0.40
Dividends declared and paid	$ 38,200,000	$ 38,900,000	$ 39,500,000