Aggregate Principal Amount of Debt Exchanged

No definition available.

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Namespace Prefix:	fnsr_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Debt Conversion, Converted Instrument, Gain (Loss) Recognized

+ References

No definition available.

+ Details

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Namespace Prefix:	fnsr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The stated principal amount of the debt instrument at time of issuance, net of debt discount originally recognized at the issuance of the instrument.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Debt Instrument, Convertible, Threshold Trading Days Within Notice of Redemption

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

The number of new shares issued in the conversion of stock in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

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-Name Accounting Standards Codification

-Topic 230

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-Section 50

-Paragraph 4

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031897-161870

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644

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-SubTopic 10

-Section 50

-Paragraph 6

-Subparagraph (b)

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-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(5))

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Conversion Rate

-URI http://asc.fasb.org/extlink&oid=6509012

+ Details

Name:	us-gaap_DebtInstrumentConvertibleConversionRatio1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

- Definition

Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 470

-SubTopic 20

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6928298&loc=SL6031898-161870

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
Period Type:	duration

- Definition

Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instruments must exceed threshold percentage for a specified number of trading days to trigger conversion feature, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentConvertibleThresholdPercentageOfStockPriceTrigger
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

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-Section 55

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-URI http://asc.fasb.org/extlink&oid=34725769&loc=d3e28878-108400

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Details

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Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph e

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of debt issuance costs (for example, but not limited to, legal, accounting, broker, and regulatory fees).

+ References

No definition available.

+ Details

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

- Details

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- Details

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- Details

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Debt - Narrative (Details) (USD $)	1 Months Ended		12 Months Ended	1 Months Ended	12 Months Ended
Debt - Narrative (Details) (USD $)	Oct. 31, 2014	Oct. 31, 2009 D	Apr. 30, 2011	Dec. 31, 2013	May 03, 2015	Apr. 27, 2014
Debt Instrument [Line Items]
Conversion of stock, shares issued	3,748,473us-gaap_ConversionOfStockSharesIssued1
Gain (loss) recognized on debt conversion	$ 0
5.0% Convertible Senior Notes Due 2029
Debt Instrument [Line Items]
Interest rate					5.00%	5.00%
0.5% Convertible Senior Notes Due 2033
Debt Instrument [Line Items]
Interest rate				0.50%	0.50%	0.50%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029
Debt Instrument [Line Items]
Debt instrument, face amount		100,000,000	40,000,000.0			40,000,000.0
Interest rate		5.00%
Convertible debt, threshold trading days		20
Convertible debt, threshold consecutive trading days		30 days
Convertible debt, threshold percentage of stock price trigger		130.00%
Convertible debt, threshold trading days within notice of redemption		5 days
Convertible debt, conversion ratio		0.0936768
Convertible debt, conversion ratio		$ 10.68
Aggregate principal amount of debt exchanged			60,000,000.0
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period Three
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period Four
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period Five
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 5.0% Convertible Senior Notes Due 2029 \| Debt Instrument, Redemption, Period Six
Debt Instrument [Line Items]
Debt redemption price percentage		100.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033
Debt Instrument [Line Items]
Debt instrument, face amount				258,800,000
Convertible debt, conversion ratio				0.0331031
Convertible debt, conversion ratio				$ 30.18
Carrying amount of liability component				209,100,000
Carrying amount of the equity component				49,600,000	49,648,000
Convertible debt, remaining discount amortization period					43 months
Debt issuance cost					3,800,000
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Debt redemption price percentage				100.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Debt redemption price percentage				100.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Redemption, Period Three
Debt Instrument [Line Items]
Debt redemption price percentage				100.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Redemption, Period Five
Debt Instrument [Line Items]
Debt redemption price percentage				100.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Conversion, Option One
Debt Instrument [Line Items]
Convertible debt, threshold trading days				20
Convertible debt, threshold consecutive trading days				30 days
Convertible debt, threshold percentage of stock price trigger				130.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Debt Instrument, Conversion, Option Two
Debt Instrument [Line Items]
Convertible debt, threshold trading days				5
Convertible debt, threshold consecutive trading days				5 days
Convertible debt, threshold percentage of stock price trigger				98.00%
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Other Noncurrent Assets
Debt Instrument [Line Items]
Debt issuance cost					3,100,000
Convertible Debt \| 0.5% Convertible Senior Notes Due 2033 \| Additional Paid-in Capital
Debt Instrument [Line Items]
Debt issuance cost					$ 725,000