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New Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2014	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment	$ (10,028)
Stock options awarded		0
Unrealized gains and losses recognized during the reporting period on equity securities	$ (4,928)
Stock Options | Chief Executive Officer | Employment Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock options awarded	0
Stock Options | Chief Executive Officer | Share-based Compensation Award, Tranche 2 | Employment Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock options awarded			300,000
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment				$ 10,000
Unrealized gains and losses recognized during the reporting period on equity securities	$ (4,928)
Accounting Standard Update 2018-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment				100
Accounting Standard Update 2017-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment	0
Stock based compensation expense	$ (300)
Accounting Standards Update 2016-16
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative-effect adjustment				$ 200

X

- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

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- Definition

The noncash expense that accounts for the value of stock or unit options distributed to employees as compensation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

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- Definition

Amount of unrealized gain (loss) recognized in the income statement on unsold other securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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