Goodwill and Intangible Assets (Weighted Average Remaining Amortization Period) (Detail)	12 Months Ended
	Dec. 31, 2020
Intellectual property
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	3 years 8 months 12 days
Customer relationships
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	1 year 6 months
Acquired methodologies and technology
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	1 year 4 months 24 days
Trade Names
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	2 months 12 days
Acquired software
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	1 month 6 days
Other
Intangible Assets [Line Items]
Weighted average remaining amortization period (in years)	3 months 18 days