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Leases (Tables) | 3 Months Ended
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Mar. 31, 2019
Leases [Abstract] |
Lease, Cost | The following table summarizes net lease expense recognized in White Mountains’s consolidated statement of operations for the three months ended March 31, 2019:
Millions Lease Cost |  | Three Months Ended March 31, 2019
Lease cost |  | $ | 1.7 |
Less: sublease income |  | .1 |
Net lease cost |  | $ | 1.6 |
Lessee, Operating Lease, Liability, Maturity | The following table presents the contractual maturities of the lease liabilities associated with White Mountains’s operating lease agreements as of March 31, 2019:
Millions |  | As of March 31, 2019
Remainder of 2019 |  | $ | 4.2 |
2020 |  | 4.6 |
2021 |  | 3.9 |
2022 |  | 3.7 |
2023 |  | 3.1 |
Thereafter |  | 5.1 |
Total undiscounted lease payments |  | 24.6 |
Less: present value adjustment |  | 2.8 |
Operating lease liability |  | $ | 21.8 |
Schedule of Right-of-Use Assets and Lease Liabilities | The following table presents lease related assets and liabilities by reportable segment as of March 31, 2019:
|  | As of March 31, 2019
Millions |  | HG/BAM |  | NSM |  | Other Operations |  | Total |  | Weighted Average Incremental Borrowing Rate (1)
ROU lease asset |  | $ | 11.8 |  |  | $ | 4.7 |  |  | $ | 5.0 |  |  | $ | 21.5 |  |  | 4.7%
Lease liability |  | $ | 11.8 |  |  | $ | 4.7 |  |  | $ | 5.3 |  |  | $ | 21.8 |  |
(1) The present value of the remaining lease payments were determined by discounting the lease payments using the incremental borrowing rate.

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- Definition Tabular disclosure of lessee's lease cost. Includes, but is not limited to, interest expense for finance lease, amortization of right-of-use asset for finance lease, operating lease cost, short-term lease cost, variable lease cost and sublease income. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980 + Details
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- Definition Tabular disclosure of undiscounted cash flows of lessee's operating lease liability. Includes, but is not limited to, reconciliation of undiscounted cash flows to operating lease liability recognized in statement of financial position. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 842 -SubTopic 20 -Section 50 -Paragraph 6 -URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980 + Details
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