Debt and Short-Term Borrowings - Summary of Total Debt (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Note payable	$ 1,000	$ 3,400
Total debt	616,740	650,759
Line of Credit | Senior Secured Credit Facility (2018 Term A) due on April 17, 2018 paying interest at a variable interest rate (London InterBank Offered Rate (“LIBOR”) plus applicable margin
Debt Instrument [Line Items]
Credit facility	$ 26,690	$ 28,721
Fixed Rate	2.25%
Line of Credit | Senior Secured Credit Facility (2018 Term A) due on April 17, 2018 paying interest at a variable interest rate (London InterBank Offered Rate (“LIBOR”) plus applicable margin | LIBOR Floor
Debt Instrument [Line Items]
Fixed Rate	2.50%	2.25%
Line of Credit | Senior Secured Credit Facility (2020 Term A) due on January 17, 2020 paying interest at a variable interest rate (LIBOR plus applicable margin
Debt Instrument [Line Items]
Credit facility	$ 200,653	$ 212,661
Line of Credit | Senior Secured Credit Facility (2020 Term A) due on January 17, 2020 paying interest at a variable interest rate (LIBOR plus applicable margin | LIBOR Floor
Debt Instrument [Line Items]
Fixed Rate	2.50%	2.50%
Line of Credit | Senior Secured Credit Facility (Term B) due on April 17, 2020 paying interest at a variable interest rate (LIBOR plus applicable margin
Debt Instrument [Line Items]
Credit facility	$ 376,395	$ 378,074
Fixed Rate	2.50%
Line of Credit | Senior Secured Credit Facility (Term B) due on April 17, 2020 paying interest at a variable interest rate (LIBOR plus applicable margin | LIBOR Floor
Debt Instrument [Line Items]
Fixed Rate	2.75%	2.50%
Minimum variable rate	0.75%	0.75%
Line of Credit | Senior Secured Revolving Credit Facility
Debt Instrument [Line Items]
Credit facility	$ 12,000	$ 28,000
Line of Credit | Senior Secured Revolving Credit Facility | LIBOR Floor
Debt Instrument [Line Items]
Fixed Rate	2.50%	2.50%
Note Payable | Note Payable due on October 1, 2017
Debt Instrument [Line Items]
Note payable	$ 0	$ 1,524
Note Payable | Note Payable due on July 31, 2017
Debt Instrument [Line Items]
Note payable	0	357
Note Payable | Note Payable due on August 31, 2019
Debt Instrument [Line Items]
Note payable	$ 584	$ 890
Fixed interest rate	7.50%	7.50%
Note Payable | Note Payable due on April 30, 2021
Debt Instrument [Line Items]
Note payable	$ 418	$ 532