Goodwill and Other Intangible Assets - Other Intangible Assets (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 648,284	$ 637,570
Accumulated amortization	(382,031)	(357,609)
Net carrying amount	266,253	279,961
Customer relationships
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	343,641	344,175
Accumulated amortization	(181,439)	(168,134)
Net carrying amount	$ 162,202	$ 176,041
Customer relationships | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	8 years	8 years
Customer relationships | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	14 years	14 years
Trademark
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 41,764	$ 41,594
Accumulated amortization	(27,103)	(25,241)
Net carrying amount	$ 14,661	$ 16,353
Trademark | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	2 years	2 years
Trademark | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	15 years	15 years
Software packages
Acquired Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 206,340	$ 195,262
Accumulated amortization	(144,277)	(136,907)
Net carrying amount	$ 62,063	$ 58,355
Software packages | Minimum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	3 years	3 years
Software packages | Maximum
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	10 years	10 years
Non-compete agreement
Acquired Finite-Lived Intangible Assets [Line Items]
Useful life in years	15 years	15 years
Gross amount	$ 56,539	$ 56,539
Accumulated amortization	(29,212)	(27,327)
Net carrying amount	$ 27,327	$ 29,212