Changes in Liability for Unrecognized Gross Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Contingency [Line Items]
Uncertain tax positions at beginning of year	$ 30,456	$ 24,779	$ 20,250
Additions for tax positions relating to current-year operations	1,304	3,827	3,515
Additions for tax positions relating to prior tax years	1,997	2,935	1,819
Subtractions for tax positions relating to prior tax years	(270)	(963)	(929)
Reductions in balance due to settlements		(122)	124
Uncertain tax positions at end of year	$ 33,487	$ 30,456	$ 24,779

Amount of increase decrease in unrecognized tax benefits resulting from settlements with taxing authorities.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

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Amount of decrease in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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Amount of increase in unrecognized tax benefits resulting from tax positions taken in prior period tax returns.

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