Debt instrument convertible conversion price denomination value.

No definition available.

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Namespace Prefix:	mx_
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Balance Type:	na
Period Type:	duration

- Definition

Senior notes pricing.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Minimum required percentage of holders to declare repurchase of notes.

+ References

No definition available.

+ Details

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- Definition

Percentage of notes to repurchased on declaration by minimum required holders.

+ References

No definition available.

+ Details

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- Definition

The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

+ References

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-Publisher FASB
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Period Type:	duration

- Definition

The price per share of the conversion feature embedded in the debt instrument.

+ References

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-Section 50
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Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Face (par) amount of debt instrument at time of issuance.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

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Period Type:	duration

- Definition

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

+ Details

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Balance Type:	debit
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt discount.

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Period Type:	instant

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The after-tax amount of interest recognized in the period associated with any convertible debt.

+ References

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Balance Type:	credit
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- Definition

The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt.

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Balance Type:	credit
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- Definition

Number of shares that have been repurchased during the period and are being held in treasury.

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- Definition

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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- Details

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Borrowings - Additional Information (Detail) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
Borrowings - Additional Information (Detail) - USD ($)	Jan. 17, 2017	Jan. 17, 2017	Jul. 18, 2013	Feb. 28, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 31, 2019
Debt Instrument [Line Items]
Repurchase of common stock, shares											1,795,444
Repurchase of common stock							$ 616,000	$ 2,588,000			$ 11,401,000
Loss on early extinguishment of long-term borrowings, net								(42,000)
6.625% Senior Notes Due 2021 [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount			$ 225,000,000
Interest rate			6.625%		6.625%		6.625%		6.625%
Due date			Jul. 15, 2021				Jul. 01, 2021		Jul. 01, 2021
Aggregate principal amount of senior notes pricing			99.50%
Debt issuance costs paid			$ 5,039,000
Interest expense related to debt					$ 3,951,000	$ 3,935,000	$ 11,838,000	$ 11,794,000
Original debt issue discount			$ 1,125,000
Debt Instrument, Repurchased Face Amount										$ 500,000		$ 250,000
Loss on early extinguishment of long-term borrowings, net							$ 21,000			28,000
6.625% Senior Notes Due 2021 [Member] \| Senior Notes [Member] \| 2019 [Member]
Debt Instrument [Line Items]
Redemption price plus accrued, unpaid interest and special interest to the date of redemption							100.00%
5.0% Exchangeable Senior Notes due March 2021 [Member] \| Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount	$ 86,250,000	$ 86,250,000
Interest rate	5.00%	5.00%			5.00%	5.00%	5.00%	5.00%	5.00%
Due date	Mar. 01, 2021						Mar. 01, 2021		Mar. 01, 2021
Aggregate principal amount of senior notes pricing		5.00%
Convertible notes principal amount denomination value							$ 1,000,000
Conversion of converted notes, shares issued							121.1387
Exchange price					$ 8.26		$ 8.26
Redemption price plus accrued, unpaid interest and special interest to the date of redemption							100.00%
Minimum required percentage of holders to declare repurchase of notes							25.00%
Percentage of notes to repurchased on declaration by minimum required holders							100.00%
Debt issuance costs paid	$ 5,902,000						$ 5,902,000
Interest expense related to the Exchangeable Notes					$ 1,429,000	$ 1,404,000	$ 4,720,000	$ 4,206,000
Debt Instrument, Repurchased Face Amount				$ 920,000						1,590,000
Loss on early extinguishment of long-term borrowings, net				$ 63,000						$ 234,000