Other expenses (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Income and Expenses [Abstract]
Investment expense (income) on deposit liabilities									$ 5,879	$ (1,273)	$ 2,800
Investment expense and change in fair value of embedded derivatives in reinsurance contracts									10,740	10,883	9,874
Other expenses	$ 3,625	$ 5,058	$ 3,811	$ 4,125	$ 2,994	$ (1,362)	$ 3,983	$ 3,995	$ 16,619	$ 9,610	$ 12,674

The net amount of other operating income and expenses, the components of which are not separately disclosed on the income statement, from items that are associated with the entity's normal revenue producing operations.

No definition available.

Name:	us-gaap_OtherOperatingIncomeExpenseNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration