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Income Taxes - Balances of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
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Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |
Unrecognized tax benefits | $ 36,229 | $ 35,240 | $ 54,541 | $ 50,668
Portion that, if recognized, would reduce tax expense and effective tax rate | 35,561 | 33,128 | 48,312 |
Accrued interest on unrecognized tax benefits | 5,368 | 5,539 | 8,750 |
Accrued penalties on unrecognized tax benefits | 631 | 650 | 673 |
Minimum |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months | 0 | 0 | 0 |
Portion that, if recognized, would reduce tax expense and effective tax rate | 0 | 0 | 0 |
Maximum |  |  |  |
Significant Change in Unrecognized Tax Benefits is Reasonably Possible [Line Items] |  |  |  |
Reasonably possible reduction to the balance of unrecognized tax benefits in succeeding 12 months | 13,655 | 12,332 | 27,485 |
Portion that, if recognized, would reduce tax expense and effective tax rate | $ 12,483 | $ 10,983 | $ 24,009 |

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- Definition Unrecognized tax benefit portion that if recognized would reduce tax expense and effective tax rate upper bound. + References No definition available. + Details
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- Definition Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (d)(3) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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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=84230637&loc=SL6600010-109319 + Details
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- Definition Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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- Definition Amount of interest expense accrued for an underpayment of income taxes. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 740 -SubTopic 10 -Section 50 -Paragraph 15 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32718-109319 + Details
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- Definition The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate. + 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 (b) -URI http://asc.fasb.org/extlink&oid=84230637&loc=SL6600010-109319 + Details
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