Fair value - Level 3 rollforward (Details) - Recurring - Significant Unobservable Inputs (Level 3) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		$ 145,572		$ 164,767
Transfers in (out) of Level 3	[1]			(22,560)
Net Purchases (Sales)		3,235	[2]	30,607
Net Unrealized Gains (Losses)	[3]	(1,807)		(677)
Net Unrealized Foreign Exchange Gains (Losses)		0		(399)
Ending balance		147,000		171,738
Term loans
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		36,048		47,479
Transfers in (out) of Level 3	[1]			0
Net Purchases (Sales)		(74)	[2]	163
Net Unrealized Gains (Losses)	[3]	(29)		(274)
Net Unrealized Foreign Exchange Gains (Losses)		0		0
Ending balance		35,945		47,368
Fixed maturities | Corporate bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		933		24,277
Transfers in (out) of Level 3	[1]			0
Net Purchases (Sales)		32	[2]	(90)
Net Unrealized Gains (Losses)	[3]	0		(69)
Net Unrealized Foreign Exchange Gains (Losses)		0		(399)
Ending balance		965		23,719
Fixed maturities | Asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance				22,560
Transfers in (out) of Level 3	[1]			(22,560)
Net Purchases (Sales)				0
Net Unrealized Gains (Losses)	[3]			0
Net Unrealized Foreign Exchange Gains (Losses)				0
Ending balance				0
Equities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Beginning balance		108,591		70,451
Transfers in (out) of Level 3	[1]			0
Net Purchases (Sales)		3,277	[2]	30,534
Net Unrealized Gains (Losses)	[3]	(1,778)		(334)
Net Unrealized Foreign Exchange Gains (Losses)		0		0
Ending balance		$ 110,090		$ 100,651

[1] During the three months ended March 31, 2019, the Company obtained pricing for an asset-backed security, for which pricing was not available as of December 31, 2018. As such, the security was transferred from Level 3 to Level 2 at its fair value as of December 31, 2018.

[2] For the three months ended March 31, 2020, the net purchases (sales) consisted of purchases of $3.3 million of equities and $32.0 thousand of corporate bonds, partially offset by calls and redemptions of $74.0 thousand of term loans. For the three months ended March 31, 2019, the net purchases (sales) consisted of purchases of $37.8 million of equities and $237.0 thousand of term loans, offset in part by sales, calls and redemptions of $7.3 million of equities, $89.9 thousand of corporate bonds and $74.0 thousand of term loans.

[3] Realized and unrealized gains or losses on Level 3 investments are included in “realized and unrealized gain (loss) on investments” in the Company’s consolidated statements of income (loss).