SEGMENT REPORTING - Reconciliation of Company's Primary Measure of Segment Profitability (EBITA) to Income from Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
EBITA	$ 191,713	$ 171,393	$ 564,168	$ 511,690
Acquisition expenses	(2,265)	(33,674)	(7,862)	(39,956)
Integration expenses	(19,162)	(13,447)	(61,008)	(31,257)
Litigation expenses	(1,481)	16,444	(5,445)	(59,006)
Changes in fair value of contingent consideration	(559)		2,085	640
Restructuring and plant conversion expenses	(491)	(2,721)	(1,661)	(18,081)
Contract exit costs	(10,110)		(22,818)
Amortization expense	(33,128)	(9,239)	(102,311)	(26,957)	$ (45,498)
Income from Operations	124,517	128,756	365,148	337,073
Other Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
EBITA	14,238	16,838	43,912	39,888
Amortization expense	(1,962)	(2,054)	(5,921)	(5,665)
Reportable Segments
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
EBITA	177,475	154,555	520,256	471,802
Reportable Segments | Domestic Regulated and Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
EBITA	163,447	132,806	479,327	401,824
Amortization expense	(24,412)	(3,634)	(67,498)	(10,319)
Reportable Segments | International Regulated and Compliance Services
Segment Reporting Reconciling Item For Operating Profit Loss From Segment To Consolidated [Line Items]
EBITA	14,028	21,749	40,929	69,978
Amortization expense	$ (6,754)	$ (3,551)	$ (28,892)	$ (10,973)