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Claim and Claim Adjustment Expense Reserves (International - Hardy - Net Cumulative Paid Claim and Claim Adjustment Expenses) (Details) - USD ($) $ in Millions | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2008 | $ 4,366 | $ 4,167 | $ 4,089 |  |  |
Total net liability for unpaid claim and claim adjustment expenses | 18,070 | 18,249 | 18,576 | $ 18,927 |  |
International |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Total net liability for unpaid claim and claim adjustment expenses | 1,432 | 1,201 |  |  |  |
Hardy | International |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 916 |  |  |  |  |
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented | 393 |  |  |  |  |
Net liability for unpaid claim and claim adjustment expenses for accident years prior to 2008 | 5 |  |  |  |  |
Liability for unallocated claim adjustment expenses for accident years presented | 8 |  |  |  |  |
Total net liability for unpaid claim and claim adjustment expenses | 406 |  |  |  |  |
Hardy | International | 2008 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 11 | 11 | 10 | 10 | $ 14 | $ 3
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented |  |  |  |  |  | 15
Hardy | International | 2009 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | (5) | (4) | (4) | (4) | (2) | 2
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented |  |  |  |  |  | 12
Hardy | International | 2010 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 49 | 48 | 46 | 43 | 36 | 19
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented |  |  |  |  |  | 39
Hardy | International | 2011 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 134 | 133 | 129 | 124 | 84 | 31
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented |  |  |  |  |  | 126
Hardy | International | 2012 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 110 | 108 | 110 | 101 | 81 | 15
Net liability for unpaid claim and allocated claim adjustment expenses for the accident years presented |  |  |  |  |  | $ 105
Hardy | International | 2013 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 133 | 129 | 123 | 103 | $ 39 |
Hardy | International | 2014 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 153 | 143 | 124 | $ 56 |  |
Hardy | International | 2015 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 131 | 99 | $ 30 |  |  |
Hardy | International | 2016 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | 147 | $ 64 |  |  |  |
Hardy | International | 2017 |  |  |  |  |  |
Short Duration Contracts Net Cumulative Paid Claim Adjustment Expenses [Line Items] |  |  |  |  |  |
Cumulative paid claims and allocated claim adjustment expense, net | $ 53 |  |  |  |  |

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- Definition Amount, after effects of reinsurance, of payments to settle claims incurred in prior periods and related claims settlement costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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- Definition Liability as of the balance sheet date for amounts representing estimated cost of settling unpaid claims under the terms of the underlying insurance policies, less estimated reinsurance recoveries on such claims. This includes an estimate for claims which have been incurred but not reported. Claim adjustment expenses represent the costs estimated to be incurred in the settlement of unpaid claims. + 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(13)(a)) -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 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (cc) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=65670824&loc=d3e14764-158437 + Details
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- Definition Amount, after reinsurance, of paid claims and allocated claim adjustment expense used in claims development for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671311-158438 + Details
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- Definition Undiscounted amount, after reinsurance, of the liability for unpaid claims and allocated claim adjustment expense for short-duration insurance contracts. Excludes unallocated claim adjustment expense. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4B -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671311-158438 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 40 -Section 50 -Paragraph 4C -URI http://asc.fasb.org/extlink&oid=65670685&loc=SL65671315-158438 + Details
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