Condensed consolidating guarantor financial information - Cash Flows (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Cash Flow Statements Captions [Line Items]
Net cash (used in) provided by operating activities from continuing operations	$ 426,301	$ 410,590	$ 303,446
Cash flows from investing activities of continuing operations:
Expenditures for property, plant and equipment	(70,903)	(53,135)	(61,448)
Payments for businesses and intangibles acquired, net of cash acquired	(1,768,284)	(14,040)	(93,808)
Proceeds from sale of businesses, assets and investments	6,332	10,201	408
Investments in affiliates	0	0	0
Net cash used in investing activities from continuing operations	(1,832,855)	(56,974)	(154,848)
Cash flows from financing activities of continuing operations:
Proceeds from new borrowings	2,463,500	671,700	288,100
Reduction in borrowings	(1,239,576)	(714,565)	(303,757)
Debt extinguishment, issuance and amendment fees	(26,664)	(8,958)	(9,017)
Proceeds from share based compensation plans and the related tax impacts	5,571	9,068	4,994
Payments to noncontrolling interest shareholders	0	(464)	(1,343)
Payments for acquisition of noncontrolling interest	0	(9,231)	0
Payments for contingent consideration	(335)	(7,282)	(8,028)
Proceeds from issuance of shares	0	0	0
Dividends	(61,237)	(58,960)	(56,532)
Intercompany transactions	0	0	0
Intercompany dividends paid	0	0	0
Net cash provided by (used in) financing activities from continuing operations	1,141,259	(118,692)	(85,583)
Cash flows from discontinued operations:
Net cash used in operating activities	(6,416)	(2,110)	(2,636)
Net cash used in discontinued operations	(6,416)	(2,110)	(2,636)
Effect of exchange rate changes on cash and cash equivalents	61,480	(27,391)	(25,249)
Net (decrease) increase in cash and cash equivalents	(210,231)	205,423	35,130
Cash and cash equivalents at the beginning of the year	543,789	338,366	303,236
Cash and cash equivalents at the end of the year	333,558	543,789	338,366
Eliminations
Condensed Cash Flow Statements Captions [Line Items]
Net cash (used in) provided by operating activities from continuing operations	(61,918)	(2,275)	(3,812)
Cash flows from investing activities of continuing operations:
Expenditures for property, plant and equipment	0	0	0
Payments for businesses and intangibles acquired, net of cash acquired	0	46,837	0
Proceeds from sale of businesses, assets and investments	(464,982)	(46,837)	0
Investments in affiliates	5,900	5,600	121,850
Net cash used in investing activities from continuing operations	(459,082)	5,600	121,850
Cash flows from financing activities of continuing operations:
Proceeds from new borrowings	0	0	0
Reduction in borrowings	0	0	0
Debt extinguishment, issuance and amendment fees	0	0	0
Proceeds from share based compensation plans and the related tax impacts	0	0	0
Payments to noncontrolling interest shareholders		0	0
Payments for acquisition of noncontrolling interest		0
Payments for contingent consideration	0	0	0
Proceeds from issuance of shares	(5,900)	(5,600)	(121,850)
Dividends	0	0	0
Intercompany transactions	464,982	0	0
Intercompany dividends paid	61,918	2,275	3,812
Net cash provided by (used in) financing activities from continuing operations	521,000	(3,325)	(118,038)
Cash flows from discontinued operations:
Net cash used in operating activities	0	0	0
Net cash used in discontinued operations	0	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0	0
Net (decrease) increase in cash and cash equivalents	0	0	0
Cash and cash equivalents at the beginning of the year	0	0	0
Cash and cash equivalents at the end of the year	0	0	0
Parent Company
Condensed Cash Flow Statements Captions [Line Items]
Net cash (used in) provided by operating activities from continuing operations	(50,585)	(85,088)	(147,704)
Cash flows from investing activities of continuing operations:
Expenditures for property, plant and equipment	(240)	(279)	(124)
Payments for businesses and intangibles acquired, net of cash acquired	(975,524)	0	0
Proceeds from sale of businesses, assets and investments	464,982	5,607	408
Investments in affiliates	0	0	0
Net cash used in investing activities from continuing operations	(510,782)	5,328	284
Cash flows from financing activities of continuing operations:
Proceeds from new borrowings	2,463,500	665,000	288,100
Reduction in borrowings	(1,239,576)	(714,565)	(303,757)
Debt extinguishment, issuance and amendment fees	(26,664)	(8,958)	(9,017)
Proceeds from share based compensation plans and the related tax impacts	5,571	9,068	4,994
Payments to noncontrolling interest shareholders		0	0
Payments for acquisition of noncontrolling interest		0
Payments for contingent consideration	0	0	0
Proceeds from issuance of shares	0	0	0
Dividends	(61,237)	(58,960)	(56,532)
Intercompany transactions	(550,579)	183,244	219,035
Intercompany dividends paid	0	0	0
Net cash provided by (used in) financing activities from continuing operations	591,015	74,829	142,823
Cash flows from discontinued operations:
Net cash used in operating activities	(6,416)	(2,110)	(1,787)
Net cash used in discontinued operations	(6,416)	(2,110)	(1,787)
Effect of exchange rate changes on cash and cash equivalents	0	0	0
Net (decrease) increase in cash and cash equivalents	23,232	(7,041)	(6,384)
Cash and cash equivalents at the beginning of the year	14,571	21,612	27,996
Cash and cash equivalents at the end of the year	37,803	14,571	21,612
Guarantor Subsidiaries
Condensed Cash Flow Statements Captions [Line Items]
Net cash (used in) provided by operating activities from continuing operations	223,373	169,400	134,817
Cash flows from investing activities of continuing operations:
Expenditures for property, plant and equipment	(34,912)	(24,753)	(32,797)
Payments for businesses and intangibles acquired, net of cash acquired	(725,554)	(10,305)	(60,336)
Proceeds from sale of businesses, assets and investments	0	49,571	0
Investments in affiliates	(5,900)	(5,600)	0
Net cash used in investing activities from continuing operations	(766,366)	8,913	(93,133)
Cash flows from financing activities of continuing operations:
Proceeds from new borrowings	0	0	0
Reduction in borrowings	0	0	0
Debt extinguishment, issuance and amendment fees	0	0	0
Proceeds from share based compensation plans and the related tax impacts	0	0	0
Payments to noncontrolling interest shareholders		0	0
Payments for acquisition of noncontrolling interest		0
Payments for contingent consideration	(335)	(7,282)	(8,028)
Proceeds from issuance of shares	0	0	121,850
Dividends	0	0	0
Intercompany transactions	551,230	(170,000)	(155,506)
Intercompany dividends paid	0	0	0
Net cash provided by (used in) financing activities from continuing operations	550,895	(177,282)	(41,684)
Cash flows from discontinued operations:
Net cash used in operating activities	0	0	0
Net cash used in discontinued operations	0	0	0
Effect of exchange rate changes on cash and cash equivalents	0	0	0
Net (decrease) increase in cash and cash equivalents	7,902	1,031	0
Cash and cash equivalents at the beginning of the year	1,031	0	0
Cash and cash equivalents at the end of the year	8,933	1,031	0
Non-Guarantor Subsidiaries
Condensed Cash Flow Statements Captions [Line Items]
Net cash (used in) provided by operating activities from continuing operations	315,431	328,553	320,145
Cash flows from investing activities of continuing operations:
Expenditures for property, plant and equipment	(35,751)	(28,103)	(28,527)
Payments for businesses and intangibles acquired, net of cash acquired	(67,206)	(50,572)	(33,472)
Proceeds from sale of businesses, assets and investments	6,332	1,860	0
Investments in affiliates	0	0	(121,850)
Net cash used in investing activities from continuing operations	(96,625)	(76,815)	(183,849)
Cash flows from financing activities of continuing operations:
Proceeds from new borrowings	0	6,700	0
Reduction in borrowings	0	0	0
Debt extinguishment, issuance and amendment fees	0	0	0
Proceeds from share based compensation plans and the related tax impacts	0	0	0
Payments to noncontrolling interest shareholders		(464)	(1,343)
Payments for acquisition of noncontrolling interest		(9,231)
Payments for contingent consideration	0	0	0
Proceeds from issuance of shares	5,900	5,600	0
Dividends	0	0	0
Intercompany transactions	(465,633)	(13,244)	(63,529)
Intercompany dividends paid	(61,918)	(2,275)	(3,812)
Net cash provided by (used in) financing activities from continuing operations	(521,651)	(12,914)	(68,684)
Cash flows from discontinued operations:
Net cash used in operating activities	0	0	(849)
Net cash used in discontinued operations	0	0	(849)
Effect of exchange rate changes on cash and cash equivalents	61,480	(27,391)	(25,249)
Net (decrease) increase in cash and cash equivalents	(241,365)	211,433	41,514
Cash and cash equivalents at the beginning of the year	528,187	316,754	275,240
Cash and cash equivalents at the end of the year	$ 286,822	$ 528,187	$ 316,754