Stockholders' Equity - Cash Dividends Declared to Stockholders (Detail) - Common Stock $ / shares in Units, $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($) $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Per Share Amount (usd per share) \| $ / shares	$ 0.375
Total Declared \| $	$ 7,627
Installment One
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Declaration Date	Feb. 28, 2018
Record Date	Mar. 16, 2018
Payment Date	Mar. 30, 2018
Per Share Amount (usd per share) \| $ / shares	$ 0.125
Total Declared \| $	$ 2,589
Installment Two
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Declaration Date	Apr. 25, 2018
Record Date	May 25, 2018
Payment Date	Jun. 22, 2018
Per Share Amount (usd per share) \| $ / shares	$ 0.125
Total Declared \| $	$ 2,538
Installment Three
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Declaration Date	Jul. 25, 2018
Record Date	Aug. 17, 2018
Payment Date	Sep. 10, 2018
Per Share Amount (usd per share) \| $ / shares	$ 0.125
Total Declared \| $	$ 2,500

Date the declared dividend will be paid, in CCYY-MM-DD format.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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Amount of paid and unpaid common stock dividends declared with the form of settlement in cash.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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The per share amount of a dividend declared, but not paid, as of the financial reporting date.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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