Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
	Nov. 02, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying amount of trading securities		$ 64,200		$ 60,100
Contingent consideration arrangement		854	$ 0
ClientTell [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration arrangement	$ 5,400	5,300		5,600
Senior Notes Due 2022 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value		982,500		862,500
Long-term debt		1,000,000		1,000,000
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		412,000
Long-term debt		400,000
Senior Secured Term Loan Facilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value		1,134,600		2,033,200
Long-term debt		1,127,200		2,063,300
Senior Secured A Term Loan [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value		669,800
Long-term debt		674,800
2019 Maturity Term Loans [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value				323,400
Long-term debt				$ 336,900
Interest Rate Swaps [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative instruments, asset		700
Derivative instruments, liability		$ 1,800