Non-life and Life and Health Reserves - Life and health reserve rollforward (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Reconciliation of Loss and Loss Expenses Including Life Policy Benefits [Line Items]
Reinsurance recoverable at beginning of year	$ 897,183
Reinsurance recoverable at end of year	889,021	$ 897,183
Life and Health
Reconciliation of Loss and Loss Expenses Including Life Policy Benefits [Line Items]
Gross liability at beginning of period	2,198,080	2,098,759	$ 1,722,330
Reinsurance recoverable at beginning of year	11,829	9,287	2,726
Net liability at beginning of period	2,186,251	2,089,472	1,719,604
Liability acquired related to the acquisition of Aurigen	0	0	67,916
Net incurred losses	1,263,016	1,024,608	835,415
Net losses paid	(1,071,487)	(818,916)	(714,151)
Effects of foreign exchange rate changes	23,081	(108,913)	180,688
Net liability at end of period	2,400,861	2,186,251	2,089,472
Reinsurance recoverable at end of year	16,183	11,829	9,287
Gross liability at end of period	$ 2,417,044	$ 2,198,080	$ 2,098,759
Minimum
Reconciliation of Loss and Loss Expenses Including Life Policy Benefits [Line Items]
Interest rate assumption related to policy benefits for life and annuity contracts	0.00%	0.00%	0.00%
Maximum
Reconciliation of Loss and Loss Expenses Including Life Policy Benefits [Line Items]
Interest rate assumption related to policy benefits for life and annuity contracts	7.00%	7.00%	7.00%

Future Policy Benefits Acquired, Aurigen

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Liability for Future Policy Benefits and Unpaid Claims and Claims Adjusment Expense, Net

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Reconciliation of Loss and Loss Expenses Including Life Policy Benefits [Line Items]

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No definition available.

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The aggregate amount of policy reserves (provided for future obligations including unpaid claims and claims adjustment expenses) and policy benefits (liability for future policy benefits) as of the balance sheet date; grouped amount of all the liabilities associated with the company's insurance policies.

+ References

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Rate of interest used to calculate the liability for future policy benefits.

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Amount of foreign currency gain (loss) which decreases (increases) the cost of settling unpaid claims after deduction of reinsurance recoveries. Includes, but is not limited to, claims which have been incurred but not reported.

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Amount, after effects of reinsurance, of expense (reversal of expense) for claims incurred and costs incurred in the claim settlement process.

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Amount, after effects of reinsurance, of payments to settle insured claims and pay costs incurred in the claims settlement process.

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Amount, after valuation allowance, recoverable under reinsurance contracts including premium paid under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

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