Leases - Supplemental Cash Flow Information Related to Operating Leases (Detail) - USD ($) $ in Thousands		9 Months Ended
Jan. 01, 2019	Sep. 30, 2019
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases		$ 3,851
Investing cash flows for operating leases		8,394
ROU assets added in exchange for lease obligations net of terminations (upon / since adoption)	$ 10,434	34,331
BRMR and Everest Merger Sub Inc. [Member]
Cash paid for amounts included in the measurement of lease liabilities:
ROU assets and lease obligations acquired in BRMR Merger		$ 7,900

Cash paid for amounts included in measurement of lease liabilities.

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- Definition

Right-of-use asset and lease obligations.

+ References

No definition available.

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- Definition

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918643-209977

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (g)(1)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

+ Details

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- Definition

Amount of cash outflow from operating lease to bring another asset to condition and location necessary for its intended use.

+ References

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- Definition

Amount of increase in right-of-use asset obtained in exchange for operating lease liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 55
-Paragraph 53
-URI http://asc.fasb.org/extlink&oid=77888399&loc=SL77918982-209971

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (g)(2)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

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