Stock-Based Compensation - Additional Information (Detail) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended		6 Months Ended
	May 03, 2021 shares	Apr. 02, 2021 Company shares	Feb. 28, 2021 TradingDay Company shares	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) $ / shares shares	Jun. 30, 2020 USD ($)
Software and Capitalized Software Costs [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Capitalized compensation cost | $				$ 1.9	$ 2.1	$ 3.4	$ 3.7
Chief Sales Officer Holly Faurot [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance share units		5,445
Number of publicly traded companies | Company		34
Restricted Stock [Member] | Share Based Compensation Award V W A P Equals Or Exceeds Five Twenty Per Share | Non Executive Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Vesting percentage, restricted shares						50.00%
VWAP Share Price | $ / shares						$ 520
Restricted Stock [Member] | Time-Based Shares [Member] | Non Executive Employees [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights						3 years
Restricted Stock [Member] | Time-Based Shares [Member] | Non Executive Employees [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation arrangement by share-based payment award, award vesting rights						4 years
Restricted Stock [Member] | Share Based Compensation Award V W A P Equals Or Exceeds Six Hundred Per Share | Non Executive Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Vesting percentage, restricted shares						50.00%
VWAP Share Price | $ / shares						$ 600
Restricted Stock [Member] | LTIP [Member] | Non-executive Employees and Non-employee Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Restricted shares of common stock issued						176,060
Restricted Stock [Member] | LTIP [Member] | Market-Based Shares [Member] | Non Executive Employees [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Restricted shares of common stock issued						42,934
Restricted Stock [Member] | LTIP [Member] | Time-Based Shares [Member] | Non-executive Employees and Non-employee Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Restricted shares of common stock issued						133,126
Restricted Stock [Member] | LTIP [Member] | Time-Based Shares [Member] | Non-Employee Members [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Restricted shares of common stock issued	3,558
Share-based compensation arrangement by share-based payment award, award vesting rights						Such shares of restricted stock will cliff-vest on the seventh day following the first anniversary of the date of grant, provided that such director is providing services to the Company through the applicable vesting date, and subject to the terms and conditions of the LTIP and the applicable restricted stock award agreement.
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Restricted shares of common stock issued						57,900
Performance Shares [Member] | LTIP [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Number of trading day | TradingDay			60
Number of publicly traded companies | Company			34
Performance Shares [Member] | LTIP [Member] | Executive Officers [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance share units			52,470
Performance Shares [Member] | LTIP [Member] | Executive Officers [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance share units			131,176
Performance Shares [Member] | LTIP [Member] | Two-Year Performance Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance period commencement date			Jan. 01, 2021
Performance period maturity date			Dec. 31, 2022
Percentage of PSUs eligible to vest			25.00%
Deadline for vesting of shares			Mar. 01, 2023
Performance Shares [Member] | LTIP [Member] | Three-Year Performance Period [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Performance period commencement date			Jan. 01, 2021
Performance period maturity date			Dec. 31, 2023
Percentage of PSUs eligible to vest			75.00%
Deadline for vesting of shares			Feb. 29, 2024
Restricted Stock Awards and PSU Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation expense | $				$ 23.8	$ 21.2	$ 47.4	$ 37.0