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Income Taxes - Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Ending Balance	$ 28,000
Federal and State [Member]
Income Tax Contingency [Line Items]
Beginning balance	23,361	$ 19,654	$ 24,213
Decrease due to prior positions		(2,044)	(7,109)
Increase due to current year position	4,216	5,448	2,550
Increase due to prior positions	379	303
Ending Balance	$ 27,956	$ 23,361	$ 19,654

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Amount of unrecognized tax benefits.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 10B
-URI http://asc.fasb.org/extlink&oid=84176650&loc=SL37586934-109318

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-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
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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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