Change of Control, Grantee Employment Termination, Vesting Period Range

No definition available.

Name:	rdn_ChangeofControlGranteeEmploymentTerminationVestingPeriodRange
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- Definition

Percentage of Board of Directors Who Oppose Change in Control to be calculated against at least a 75% change in the Board of directors to ultimately define a change in control event.

+ References

No definition available.

+ Details

Name:	rdn_PercentageOfBoardOfDirectorsWhoOpposeChangeInControl
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of Change in Members of Board of Directors Defined As Change in Control to be calculated against the number of members who did not approve the change in control (need 75% of Board that voted against the change to consider the event a change in control).

+ References

No definition available.

+ Details

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

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan without adjustment for ratio of shares beyond 1 for 1.

+ References

No definition available.

+ Details

Name:	rdn_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantExcludingAdjustments
Namespace Prefix:	rdn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Vesting Percentage of Total Award, Fourth Anniversary

+ References

No definition available.

+ Details

Name:	rdn_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentageOfTotalAwardFourthAnniversary
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Vesting Percentage of Total Award, Third Anniversary

+ References

No definition available.

+ Details

Name:	rdn_ShareBasedCompensationArrangementByShareBasedPaymentAwardVestingPercentageOfTotalAwardThirdAnniversary
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

This concept represents the maximum contractual term in PnYnMnD format for share-based payment awards.

+ References

No definition available.

+ Details

Name:	rdn_SharebasedCompensationArrangementMaximumContractualTerm
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of month period used in calculating change in control as it relates to share-based compensation plans.

+ References

No definition available.

+ Details

Name:	rdn_SharebasedCompensationArrangementsNumberofMonthsRollingUsedForCalculationofChangeinControl
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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation by Share-based Payment Award, Percentage of Outstanding Common Stock Acquired, Threshold for Options Becoming Vested under a change in control situation.

+ References

No definition available.

+ Details

Name:	rdn_ShareBasedCompensationByShareBasedPaymentAwardPercentageOfOutstandingCommonStockAcquiredThresholdForOptionsBecomingVestedUnderChangeInControlDefinition
Namespace Prefix:	rdn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Share-based Compensation, Reduction of Shares Available for Grant by Each Grant of Equity Award

+ References

No definition available.

+ Details

Name:	rdn_ShareBasedCompensationReductionOfSharesAvailableForGrantByEachGrantOfEquityAward
Namespace Prefix:	rdn_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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

- Details

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

- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(3)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=rdn_EquityCompensationPlan2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=rdn_EquityCompensationPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=rdn_GrantsAwardedFromMay132009andForwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Note 15 - Share-Based and Other Compensation Plans (Awards Summary - Textual) (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares remaining available for grant (shares reserve)	4,258,907
Equity Compensation Plan, 2014 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock authorized for issuance	6,416,180
Number of shares remaining available for grant (shares reserve)	4,240,002
Share-based Compensation Arrangement By Share-based Payment Award Number of Shares Available for Grant Excluding Adjustments	4,728,559
Equity Compensation Plan, 2014 [Member] \| Restricted Stock, Restricted Stock Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation, Reduction of Shares Available for Grant by Each Grant of Equity Award	1.31
Equity Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum contractual term for all awards	10 years
Change of control, estimated pre-tax accounting charge, acceleration of compensation expense	$ 17.5	$ 31.9	$ 22.4
Equity Compensation Plans [Member] \| Restricted Stock, Restricted Stock Units and Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Vesting Percentage of Total Award, Third Anniversary	100.00%
Equity Compensation Plans [Member] \| Stock Options and SARs [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Vesting Percentage of Total Award, Third Anniversary	50.00%
Share-based Compensation Arrangement by Share-based Payment Award, Vesting Percentage of Total Award, Fourth Anniversary	50.00%
Grants Awarded Prior to May 13 2009 [Member] \| Equity Compensation Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Third party minimum threshold percentage acquisition of outstanding common stock	40.00%
Share-based Compensation Arrangements, Number of Months (Rolling) Used For Calculation of Change in Control	24 months
Percentage of Change in Members of Board of Directors Defined As Change in Control	75.00%
Percentage of Board of Directors Who Oppose Change in Control	75.00%
Grants Awarded Prior to May 13 2009 [Member] \| Equity Compensation Plan, 1995
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Third party minimum threshold percentage acquisition of outstanding common stock	20.00%
Grants Awarded From May 13 2009 and Forward [Member] \| Equity Compensation Plans [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Change of control, grantee employment termination, vesting period range (in days and years)	90 days
Grants Awarded From May 13 2009 and Forward [Member] \| Equity Compensation Plans [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Change of control, grantee employment termination, vesting period range (in days and years)	1 year