Related Party Transactions - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 31, 2008	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Other Related Party Transactions [Line Items]
Duration of lease	20 years
John H. Sykes [Member]
Schedule of Other Related Party Transactions [Line Items]
Payment to landlord under the lease terms		$ 100,000	$ 100,000	$ 200,000	$ 200,000
Related party transaction, description				In January 2008, the Company entered into a lease for a customer engagement center located in Kingstree, South Carolina. The landlord, Kingstree Office One, LLC, is an entity controlled by John H. Sykes, the founder, former Chairman and former Chief Executive Officer of the Company and the father of Charles Sykes, President and Chief Executive Officer of the Company. The lease payments on the 20-year lease were negotiated at or below market rates, and the lease is cancellable at the option of the Company.
Equity Method Investee [Member] | XSell Technologies Inc [Member]
Schedule of Other Related Party Transactions [Line Items]
Related party transaction, description				The Company contracted to receive services from XSell, an equity method investee, for $0.1 million during the three months ended June 30, 2018 (none in 2019), and less than $0.1 million and $0.1 million during the six months ended June 30, 2019 and 2018, respectively.  These related party transactions occurred in the normal course of business on terms and conditions that are similar to those of transactions with unrelated parties and, therefore, were measured at the exchange amount.
Related party transaction with equity method investee		$ 0	$ 100,000		$ 100,000
Equity Method Investee [Member] | XSell Technologies Inc [Member] | Maximum [Member]
Schedule of Other Related Party Transactions [Line Items]
Related party transaction with equity method investee				$ 100,000