Allowance for Expected Credit Losses - Contractholder receivables (Details) - USD ($) $ in Thousands		3 Months Ended	6 Months Ended
		Jun. 30, 2020	Jun. 30, 2020
Credit Loss [Abstract]
Balance at beginning of period		$ 2,140,724	$ 2,119,460
Balance at end of period		2,179,124	2,179,124
Allowance for Expected Credit Losses
Balance at beginning of period		9,038	0
Cumulative effect of accounting change (1)	[1]	0	6,663
Change for provision of expected credit losses		(2,748)	(373)
Balance at end of period		$ 6,290	$ 6,290

[1] Adoption of ASU 2016-13, “Financial Instruments - Credit Losses (Topic 326)”