Investments - Schedule of other than temporary impairments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	$ 3,000	$ 1,210	$ 4,806	$ 8,084
Credit loss impairments | Fixed maturities
Schedule of Available-for-sale Securities [Line Items]
OTTI on investments, net of amounts transferred to other comprehensive income	748	162	1,513	388
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	0	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	3,000	1,210	4,806	8,084	[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	$ 2,252	$ 1,048	$ 3,293	$ 2,721

[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 noted in Note 1(b), "Significant Accounting Policies - Recent Accounting Pronouncements," the movements on these investments are now shown separately.