Reconciliation of U.S. Statutory Federal Income Tax Rate and Effective Income Tax Rate (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Statutory Federal Tax Rate [Line Items]
Statutory income tax rate	19.25%	20.00%	35.00%
Effects of:
State income taxes, net of federal benefit	11.00%	(16.60%)	5.20%
Acquired deferred tax assets			5.80%
U.S. domestic manufacturing deduction	(0.90%)	(12.00%)
Facilitative transaction costs	54.20%	22.00%
Research and development tax credits	(119.70%)	(90.60%)	(25.10%)
Withholding taxes (U.K. entities)	12.40%	245.50%
U.K. stamp duty		9.40%
Subpart F income		4.00%	4.80%
Changes in valuation allowance	35.10%	6.00%	(26.60%)
Foreign tax credits	29.50%	(14.00%)	(20.70%)
Non-deductible officer compensation	4.90%		5.30%
Benefit of other foreign tax regimes	(170.60%)	(135.40%)
Recapture of dual consolidated losses			1.10%
Taiwan gain			34.30%
Change in tax rate	(105.00%)
Uncertain tax positions	(13.10%)	88.90%	(1.70%)
Other, net	5.00%	(13.50%)	8.70%
Effective Income Tax Rate Reconciliation, Percent, Total	(211.85%)	62.80%	21.10%
Non-US
Effects of:
Foreign tax rate differential			(5.00%)
Other Foreign
Effects of:
Foreign tax rate differential	26.10%	(50.90%)