Stock-Based Compensation (Valuation Assumptions) (Details) - Stock Appreciation Rights (SARs) [Member]	12 Months Ended
Dec. 31, 2020 $ / shares
1/24/2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Year	2020
Grant Date	Jan. 24, 2020
Expected Life	5 years 1 month 6 days
Expected Volatility	66.33%
Expected Dividend Yield	0.00%
Risk Free Interest Rate	0.37%
Fair Value Per Award	$ 1.52
3/9/2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Year	2020
Grant Date	Mar. 09, 2020
Expected Life	5 years 2 months 12 days
Expected Volatility	66.06%
Expected Dividend Yield	0.00%
Risk Free Interest Rate	0.38%
Fair Value Per Award	$ 1.61
9/14/2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Year	2020
Grant Date	Sep. 14, 2020
Expected Life	5 years 8 months 12 days
Expected Volatility	64.76%
Expected Dividend Yield	0.00%
Risk Free Interest Rate	0.44%
Fair Value Per Award	$ 1.45
11/30/2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant Year	2020
Grant Date	Nov. 30, 2020
Expected Life	5 years 10 months 24 days
Expected Volatility	64.06%
Expected Dividend Yield	0.00%
Risk Free Interest Rate	0.46%
Fair Value Per Award	$ 1.34

Grant date.

No definition available.

Name:	rail_GrantDate
Namespace Prefix:	rail_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Grant year.

+ References

No definition available.

+ Details

Name:	rail_GrantYear
Namespace Prefix:	rail_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Fair Value Per Award

+ References

No definition available.

+ Details

Name:	rail_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsFairValuePerAward
Namespace Prefix:	rail_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

+ References

+ Details

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

- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ References

+ Details

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

- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

+ Details

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

- 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

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Expected term of award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 14.D.2)
-URI http://asc.fasb.org/extlink&oid=115993241&loc=d3e301413-122809

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_StockAppreciationRightsSARSMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=rail_DateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=rail_DateBMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=rail_DateCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardDateAxis=rail_GrantDateDMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: