Losses and Loss Expenses (Tables)

3 Months Ended

Mar. 31, 2018

Liability for Claims and Claims Adjustment Expense [Abstract]

Reconciliation of the beginning and ending balances of unpaid losses and loss expenses

The following table represents a reconciliation of the beginning and ending balances of unpaid losses and loss expenses, including an analysis of the Company's paid and unpaid losses and loss expenses incurred for the years indicated:

(U.S. dollars in thousands)	2018			2017
Unpaid losses and loss expenses at the beginning of the year	$	29,696,779		$	25,939,571
Unpaid losses and loss expenses recoverable at the beginning of the year (1)	7,239,446			5,480,300
Net unpaid losses and loss expenses at the beginning of the year	$	22,457,333		$	20,459,271
Increase (decrease) in net losses and loss expenses incurred in respect of losses occurring in:
Current year	1,631,142			1,559,452
Prior year	(9,136		)	24,004
Total net incurred losses and loss expenses	$	1,622,006		$	1,583,456
Foreign exchange and other	262,571			56,244
Less net losses and loss expenses paid in respect of losses occurring in:
Current year	128,691			106,472
Prior year	1,774,194			1,222,119
Total net paid losses	$	1,902,885		$	1,328,591
Net unpaid losses and loss expenses at March 31	22,439,025			20,770,380
Unpaid losses and loss expenses recoverable at March 31 (1)	7,262,543			5,674,744
Unpaid losses and loss expenses at March 31	$	29,701,568		$	26,445,124

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(1) P&C business only, net of provision for uncollectible reinsurance.

Segment Reporting Information [Line Items]

Net (favorable) adverse prior year loss development

The following table presents the net (favorable) adverse prior year loss development of the Company's loss and loss expense reserves for its P&C operations by operating segment for each of the years indicated:

	Three Months Ended
	March 31,
(U.S. dollars in thousands)	2018			2017
Insurance segment	$	(5,295	)	$	(4,642	)
Reinsurance segment	(3,841		)	28,646
Total	$	(9,136	)	$	24,004

Insurance Segment

Segment Reporting Information [Line Items]

Net (favorable) adverse prior year loss development

The following table summarizes the net (favorable) adverse prior year reserve development by product type relating to the Insurance segment for the three months ended March 31, 2018 and 2017:

	Three Months Ended
	March 31,
(U.S. dollars in thousands)	2018			2017
Professional	$	(1,830	)	$	(5	)
Casualty	(5,115		)	(4,770		)
Property	1,257			81
Specialty	393			52
Total	$	(5,295	)	$	(4,642	)

Reinsurance Segment

Segment Reporting Information [Line Items]

Net (favorable) adverse prior year loss development

The following table summarizes the net (favorable) adverse prior year reserve development by line of business relating to the Reinsurance segment for the three months ended March 31, 2018 and 2017:

	Three Months Ended
	March 31,
(U.S. dollars in thousands)	2018			2017
Property and other short-tail lines	$	(18,994	)	$	(54,916	)
Casualty and other long-tail lines	15,153			83,562
Total	$	(3,841	)	$	28,646