Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Thousands		12 Months Ended
	Nov. 02, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying amount of trading securities		$ 63,500	$ 60,100
Contingent consideration arrangement		1,099	234	$ 0
ClientTell [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Contingent consideration arrangement	$ 5,400	4,600	5,600
Contingent consideration, fair value adjustment		1,100
Business acquisition contingent consideration paid		2,100
Senior Secured Term Loan Facilities [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Long-term debt, fair value		1,128,600	2,033,200
Long-term debt		1,124,400	2,063,300
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		411,500
Long-term debt		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		967,500	862,500
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		649,800
Long-term debt		650,700
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		14,500
Derivative instruments, liability		$ 300