Investments - Schedule of other than temporary impairments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	$ 1,806	$ 6,874
Credit loss impairments | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	765	226
Impaired more than 11 months or more than 50% | Equities and other investments
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	0	4,975
Excluding Life Funds Withheld Assets
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	1,806	6,874	[1]
Excluding Life Funds Withheld Assets | Currency losses
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	$ 1,041	$ 1,673

[1] AFS in the prior year includes net realized gains (losses) on equity securities and other investments. Due to the implementation of ASU 2016-01, as described in in Note 1(b), "Significant Accounting Policies - Recent Accounting Pronouncements," the net realized gains (losses) on these investments are shown separately.