Share-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares		Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	43,032
Unrecognized compensation expense related to the awards to Non employee directors | $	$ 4,300
Share-based Compensation Arrangement by Share-based Payment Award, Accelerated Vesting, Number	14,107
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Forfeitures and Expirations	2,569
Shares reserved for issuance	831,183
Number of Shares, Granted	751		792
Number of shares withheld	7,635		16,918	10,269
Payments of employees' tax obligations to taxing authorities	3
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount | $	$ 1,100
SICP Awards to Non-employee directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Amortization of expense equally over a service period	1 year
Unrecognized compensation expense related to the awards to Non employee directors | $	$ 200
Weighted average grant-date fair value of awards granted | $ / shares	$ 93.14		$ 75.70
Total [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	6,759		7,128
Awards to non-employee director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Granted	254		276
Weighted average grant-date fair value of awards granted | $ / shares	$ 95.83		$ 81.30
SICP Awards to Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value | $ / shares	$ 67,080.00		$ 47.39
Number of Shares, Granted	88,048	[1]	49,494
Weighted average grant-date fair value of awards granted | $ / shares	$ 92,740	[1]	$ 67.76
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Nonvested | $	$ 15,100		$ 10,700	$ 10,400
Stock and Incentive Compensation Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for issuance	449,868

[1] Includes 43,032 shares that were granted to certain key employees in December 2019 associated with their promotion