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Commitments, Contingencies and Off-Balance Sheet Arrangements - Outstanding Letters of Credit, Financial Guarantees and Funding Commitments (Detail) $ in Millions | 12 Months Ended
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Dec. 31, 2017 USD ($)
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Maximum Exposure | $ 19.7
Liability Recorded | $ 13.5
Funding Commitment To One Fund - Funded In January 2018 [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | None
Compensation to Us | None
Maximum Exposure | $ 0.4
Credit Support Under Letters Of Credit For Deductibles Due By Us On Our Own Insurance Coverage's Expires After 2022 [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | None
Compensation to Us | None
Maximum Exposure | $ 9.7
Liability Recorded | $ 12.8
Credit Enhancement Under Letters Of Credit For Our Captive Insurance Operations To Meet Minimum Statutory Capital Requirements Expires After 2022 [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | None
Compensation to Us | Reimbursement of LOC fees
Maximum Exposure | $ 6.3
Credit Support for Our Obligation Under a Client's Insurance Program Expires 2018 [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | None
Compensation to Us | None
Maximum Exposure | $ 0.7
Liability Recorded | $ 0.7
Credit Support Under Letters of Credit in Lieu of Security Deposit for Acquisition Lease Expires 2023 [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | None
Compensation to Us | None
Maximum Exposure | $ 0.5
Financial Guarantees of Loans to Nineteen Canadian Based Employees Trigger [Member] |
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items] |
Collateral | -1
Compensation to Us | None
Maximum Exposure | $ 2.1

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- Definition Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 Reference 3: 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)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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