XML 14 R48.htm IDEA: XBRL DOCUMENT v2.4.0.6

Investment Securities (Details 8) (USD $) In Millions, unless otherwise specified																																																																																			3 Months Ended				3 Months Ended
	Mar. 31, 2012 Fair Value	Dec. 31, 2011 Fair Value	Mar. 31, 2011 Fair Value	Dec. 31, 2010 Fair Value	Mar. 31, 2012 Level 2 Inputs	Dec. 31, 2011 Level 2 Inputs	Mar. 31, 2011 Level 2 Inputs	Dec. 31, 2010 Level 2 Inputs	Mar. 31, 2012 Mortgage-backed and asset-backed securities Fair Value	Dec. 31, 2011 Mortgage-backed and asset-backed securities Fair Value	Mar. 31, 2012 Mortgage-backed and asset-backed securities Level 2 Inputs	Dec. 31, 2011 Mortgage-backed and asset-backed securities Level 2 Inputs	Mar. 31, 2012 Mortgage-backed and asset-backed securities Level 3 Inputs	Dec. 31, 2011 Mortgage-backed and asset-backed securities Level 3 Inputs	Mar. 31, 2012 Mortgage-backed securities Fair Value	Dec. 31, 2011 Mortgage-backed securities Fair Value	Mar. 31, 2012 Mortgage-backed securities Level 2 Inputs	Dec. 31, 2011 Mortgage-backed securities Level 2 Inputs	Mar. 31, 2012 Mortgage-backed securities Level 3 Inputs	Dec. 31, 2011 Mortgage-backed securities Level 3 Inputs	Mar. 31, 2012 Agency mortgage-backed securities Fair Value	Dec. 31, 2011 Agency mortgage-backed securities Fair Value	Mar. 31, 2012 Agency mortgage-backed securities Level 2 Inputs	Dec. 31, 2011 Agency mortgage-backed securities Level 2 Inputs	Mar. 31, 2012 Agency mortgage-backed securities Level 3 Inputs	Mar. 31, 2012 GNMA Fair Value	Dec. 31, 2011 GNMA Fair Value	Mar. 31, 2012 GNMA Level 2 Inputs	Dec. 31, 2011 GNMA Level 2 Inputs	Mar. 31, 2012 FNMA Fair Value	Dec. 31, 2011 FNMA Fair Value	Mar. 31, 2012 FNMA Level 2 Inputs	Dec. 31, 2011 FNMA Level 2 Inputs	Mar. 31, 2012 FHLMC Fair Value	Dec. 31, 2011 FHLMC Fair Value	Mar. 31, 2012 FHLMC Level 2 Inputs	Dec. 31, 2011 FHLMC Level 2 Inputs	Mar. 31, 2012 FHLMC Level 3 Inputs	Mar. 31, 2012 Non-agency mortgage-backed securities 2003	Mar. 31, 2012 Non-agency mortgage-backed securities 2006	Mar. 31, 2012 Non-agency mortgage-backed securities 2007	Mar. 31, 2012 Non-agency mortgage-backed securities 2009	Mar. 31, 2012 Non-agency mortgage-backed securities 2010	Mar. 31, 2012 Non-agency mortgage-backed securities 2011	Mar. 31, 2012 Non-agency mortgage-backed securities 2012	Mar. 31, 2012 Non-agency mortgage-backed securities Fair Value	Dec. 31, 2011 Non-agency mortgage-backed securities Fair Value	Mar. 31, 2012 Non-agency mortgage-backed securities Level 2 Inputs	Dec. 31, 2011 Non-agency mortgage-backed securities Level 2 Inputs	Mar. 31, 2012 Non-agency mortgage-backed securities Level 3 Inputs	Dec. 31, 2011 Non-agency mortgage-backed securities Level 3 Inputs	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Super Senior	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Super Senior Prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Super Senior Non-prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Senior	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Senior Prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Senior Non-prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) 2003	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) 2006	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) 2007	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) 2010	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) 2011	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Fair Value	Dec. 31, 2011 Non-agency residential mortgage-backed securities (RMBS) Fair Value	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Fair Value Prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Fair Value Non-prime	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Level 2 Inputs	Dec. 31, 2011 Non-agency residential mortgage-backed securities (RMBS) Level 2 Inputs	Mar. 31, 2012 Non-agency residential mortgage-backed securities (RMBS) Level 3 Inputs	Dec. 31, 2011 Non-agency residential mortgage-backed securities (RMBS) Level 3 Inputs	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) Super Senior	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) Senior	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) 2007	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) 2009	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) 2010	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) 2011	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) 2012	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) Fair Value	Dec. 31, 2011 Non-agency commercial mortgage-backed securities (CMBS) Fair Value	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) Level 2 Inputs	Dec. 31, 2011 Non-agency commercial mortgage-backed securities (CMBS) Level 2 Inputs	Mar. 31, 2012 Non-agency commercial mortgage-backed securities (CMBS) Maximum	Mar. 31, 2012 Fixed Rate CMBS	Mar. 31, 2012 Fixed Rate CMBS Super Senior	Mar. 31, 2012 Fixed Rate CMBS Senior	Mar. 31, 2012 Fixed Rate CMBS Fair Value	Mar. 31, 2012 Floating Rate CMBS	Mar. 31, 2012 Floating Rate CMBS Super Senior	Mar. 31, 2012 Floating Rate CMBS Senior	Mar. 31, 2012 Floating Rate CMBS Fair Value	Mar. 31, 2012 Other asset-backed securities Fair Value	Dec. 31, 2011 Other asset-backed securities Fair Value	Mar. 31, 2012 Other asset-backed securities Level 2 Inputs	Dec. 31, 2011 Other asset-backed securities Level 2 Inputs	Mar. 31, 2012 Credit card receivables Fair Value	Dec. 31, 2011 Credit card receivables Fair Value	Mar. 31, 2012 Credit card receivables Level 2 Inputs	Dec. 31, 2011 Credit card receivables Level 2 Inputs	Mar. 31, 2012 Vehicle receivables Fair Value	Dec. 31, 2011 Vehicle receivables Fair Value	Mar. 31, 2012 Vehicle receivables Level 2 Inputs	Dec. 31, 2011 Vehicle receivables Level 2 Inputs	Mar. 31, 2012 Other Fair Value	Dec. 31, 2011 Other Fair Value	Mar. 31, 2012 Other Level 2 Inputs	Dec. 31, 2011 Other Level 2 Inputs
Mortgage-backed, Asset-backed Securities Abstract
Average basis points of subordination (as a percent)																																																																																			0.002				0.0045
Percentage of underlying loans reported as non-performing																																																																																		1.00%
Fair value investments	$ 7,583.8	$ 8,346.8	$ 7,784.8	$ 7,901.6	$ 5,115.0	$ 6,088.2	$ 5,498.5	$ 5,477.4	$ 2,151.2	$ 3,222.9	$ 2,062.9	$ 3,207.8	$ 88.3	$ 15.1	$ 1,995.5	$ 2,474.1	$ 1,907.2	$ 2,459.0	$ 88.3	$ 15.1	$ 1,614.9	$ 2,114.3	$ 1,541.7	$ 2,114.3	$ 73.2	$ 1,200.3	$ 1,365.8	$ 1,200.3	$ 1,365.8	$ 308.2	$ 712.6	$ 308.2	$ 712.6	$ 106.4	$ 35.9	$ 33.2	$ 35.9	$ 73.2	$ 2.9	$ 22.7	$ 43.1	$ 11.3	$ 16.8	$ 266.6	$ 17.2	$ 380.6	$ 359.8	$ 365.5	$ 344.7	$ 15.1	$ 15.1	$ 33.4	$ 18.3	$ 15.1	$ 48.1	$ 47.4	$ 0.7	$ 2.9	$ 22.7	$ 25.4	$ 10.5	$ 20.0	$ 81.5	$ 83.1	$ 65.7	$ 15.8	$ 66.4	$ 68.0	$ 15.1	$ 15.1	$ 80.5	$ 218.6	$ 17.7	$ 11.3	$ 6.3	$ 246.6	$ 17.2	$ 299.1	$ 276.7	$ 299.1	$ 276.7			$ 62.8	$ 208.7	$ 271.5		$ 17.7	$ 9.9	$ 27.6	$ 155.7	$ 748.8	$ 155.7	$ 748.8	$ 81.5	$ 380.6	$ 81.5	$ 380.6	$ 43.0	$ 345.6	$ 43.0	$ 345.6	$ 31.2	$ 22.6	$ 31.2	$ 22.6

X

- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents investment securities as of the balance sheet date which may include marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Available-for-Sale Securities

-URI http://asc.fasb.org/extlink&oid=6505594



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6379932&loc=d3e22054-111558



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 13

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Trading Securities

-URI http://asc.fasb.org/extlink&oid=6526789



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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 12

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 7

-Section 03

-Paragraph 1

-Subparagraph a, f, g



Reference 7: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 35

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6956420&loc=d3e24584-111560

+ Details

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Balance Type:	debit
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X

- Definition

Reflects the percentage derived from dividing impaired loans on which interest has ceased to be accrued by total loans.

+ References

No definition available.

+ Details

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

X

- Definition

Basis points of subordination on average.

+ References

No definition available.

+ Details

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Namespace Prefix:	wtm_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	duration

X

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
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