Investment Information - Allowance for expected credit losses (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Allowance for expected credit losses
Balance at beginning of period		$ 0
Cumulative effect of accounting change		634
Additions for current-period provision for expected credit losses		9,349
Additions (reductions) for previously recognized expected credit losses		(23)
Reductions due to disposals		(22)
Write-offs charged against the allowance		0
Balance at end of period		9,938
Fixed maturities
Allowance for expected credit losses
Balance at beginning of period		0
Additions for current-period provision for expected credit losses		9,320	$ 0
Balance at end of period		9,909
Fixed maturities | Asset backed securities
Allowance for expected credit losses
Balance at beginning of period		0
Cumulative effect of accounting change	[1]	517
Additions for current-period provision for expected credit losses	[1]	2,146
Additions (reductions) for previously recognized expected credit losses	[1]	(2)
Reductions due to disposals	[1]	(7)
Write-offs charged against the allowance	[1]	0
Balance at end of period		2,654
Fixed maturities | Municipal bonds
Allowance for expected credit losses
Balance at beginning of period		0
Cumulative effect of accounting change		0
Additions for current-period provision for expected credit losses		23
Additions (reductions) for previously recognized expected credit losses		0
Reductions due to disposals		0
Write-offs charged against the allowance		0
Balance at end of period		23
Fixed maturities | Corporate bonds
Allowance for expected credit losses
Balance at beginning of period		0
Cumulative effect of accounting change		117
Additions for current-period provision for expected credit losses		7,151
Additions (reductions) for previously recognized expected credit losses		(21)
Reductions due to disposals		(15)
Write-offs charged against the allowance		0
Balance at end of period		7,232
Short-term investments
Allowance for expected credit losses
Balance at beginning of period		0
Cumulative effect of accounting change		0
Additions for current-period provision for expected credit losses		29
Additions (reductions) for previously recognized expected credit losses		0
Reductions due to disposals		0
Write-offs charged against the allowance		0
Balance at end of period	[2]	$ 29

[1] Includes asset backed securities, mortgage backed securities and commercial mortgage backed securities.

[2] Effective January 1, 2020, the Company adopted ASU 2016-13 and as a result any credit impairment losses on the Company’s available-for-sale investments are recorded as an allowance, subject to reversal.