Reconciliation of Net Income To Adjusted Segment Earnings before Interest, Taxes, Depreciation and Amortization (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting [Abstract]
Net income	$ 7,101	$ 21,691	$ 26,547	$ 30,181	$ 10,349	$ 10,309	$ 21,709	$ 23,686	$ 85,520	$ 66,053	$ 58,807
Income tax provision	(1,832)	10,292	15,437	18,386	7,577	6,177	13,922	11,657	42,283	39,333	42,604
Interest income and other	(571)	(3,213)	(4,125)	(2,557)	(392)	(2,027)	(950)	137	(10,466)	(3,232)	(4,670)
Interest expense	$ 5,983	$ 6,304	$ 6,303	$ 6,229	$ 6,231	11,696	$ 12,473	$ 12,368	24,819	42,768	50,685
Loss on early extinguishment of debt						$ 19,589				19,589
Unallocated corporate expenses									88,182	81,348	84,545
Segment depreciation expense									34,064	27,717	30,267
Amortization of intangible assets									10,306	11,726	15,521
Segment special charges									9,833		16,339
Remeasurement of acquisition-related contingent consideration									1,403	(1,867)	(2,723)
Adjusted Segment EBITDA									$ 285,944	$ 283,435	$ 291,375