Goodwill and Intangible Assets - Intangible Assets (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Intangible assets
Gross Carrying Amount	$ 120,697	$ 125,221
Accumulated Amortization	98,447	93,596
Customer Relationships [Member]
Intangible assets
Gross Carrying Amount	83,287	87,577
Accumulated Amortization	$ 64,757	61,882
Customer Relationships [Member] | Minimum
Intangible assets
Useful Life  (in years)	3 years
Customer Relationships [Member] | Maximum
Intangible assets
Useful Life  (in years)	13 years
Trade Names [Member]
Intangible assets
Gross Carrying Amount	$ 28,930	28,930
Accumulated Amortization	$ 26,788	25,894
Trade Names [Member] | Minimum
Intangible assets
Useful Life  (in years)	5 years
Trade Names [Member] | Maximum
Intangible assets
Useful Life  (in years)	6 years
Technology And Software [Member]
Intangible assets
Useful Life  (in years)	5 years
Gross Carrying Amount	$ 5,800	5,694
Accumulated Amortization	$ 5,053	4,321
Noncompete Agreements [Member]
Intangible assets
Useful Life  (in years)	5 years
Gross Carrying Amount	$ 1,880	2,220
Accumulated Amortization	$ 1,441	1,447
Customer Contracts [Member]
Intangible assets
Useful Life  (in years)	2 years
Gross Carrying Amount	$ 800	800
Accumulated Amortization	$ 408	$ 52