Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying amount of trading securities	$ 69,700		$ 63,500
Contingent consideration arrangement	645	$ 644
ClientTell [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration arrangement	5,300		4,600
Senior Secured Term Loan Facilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value	1,120,100		1,128,600
Long-term debt	1,118,700		1,124,400
Senior Notes Due 2021 [Member] | Senior Notes [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value	408,000		411,500
Long-term debt	400,000		400,000
Senior Notes Due 2022 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value	1,010,000		967,500
Long-term debt	1,000,000		1,000,000
Senior Secured A Term Loan [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value	628,900		649,800
Long-term debt	629,700		650,700
Interest Rate Swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, asset	12,000		14,500
Derivative instruments, liability	$ 200		$ 300