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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
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Stock-Based Compensation - Additional Information (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options granted	200,000	0	0
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	3 years
Contractual terms	10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	4 years
Restricted Stock [Member] \| Minimum [Member] \| Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	3 years
Restricted Stock [Member] \| Minimum [Member] \| Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	1 year
Restricted Stock [Member] \| Maximum [Member] \| Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	4 years
Restricted Stock [Member] \| Maximum [Member] \| Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for stock options and restricted stock	3 years