Fair Value - Rollforward of Level 3 assets and liabilities (Details) - Recurring - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Contingent consideration liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		$ (7,998)	$ (66,665)
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	(54)	(908)
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0
Purchases, issuances, sales and settlements
Purchases		0	0
Issuances		0	(548)
Sales		0	0
Settlements		85	0
Transfers in and/or out of Level 3		0	0
Balance at end of period		(7,967)	(68,121)
Available for sale | Structured securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	[2]	5,216	313
Total gains or (losses) (realized/unrealized) - included in earnings	[1],[2]	9	1,757
Total gains or (losses) (realized/unrealized) - included in other comprehensive income	[2]	(22)	4
Purchases, issuances, sales and settlements
Purchases	[2]	0	0
Issuances	[2]	0	0
Sales	[2]	0	(1,757)
Settlements	[2]	(1,357)	(15)
Transfers in and/or out of Level 3	[2]	0	0
Balance at end of period	[2]	3,846	302
Available for sale | Corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		8,851	8,141
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	7	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		(5,416)	(118)
Purchases, issuances, sales and settlements
Purchases		0	0
Issuances		0	0
Sales		0	0
Settlements		(1,462)	(456)
Transfers in and/or out of Level 3		0	0
Balance at end of period		1,980	7,567
Fair value option | Corporate bonds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		932	5,758
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	0	(290)
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0
Purchases, issuances, sales and settlements
Purchases		33	0
Issuances		0	0
Sales		0	(3,235)
Settlements		0	0
Transfers in and/or out of Level 3		0	0
Balance at end of period		965	2,233
Fair value option | Other investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		68,817	62,705
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	(27)	298
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0
Purchases, issuances, sales and settlements
Purchases		21	0
Issuances		0	0
Sales		(17,175)	(74)
Settlements		0	(600)
Transfers in and/or out of Level 3		2,984	0
Balance at end of period		54,620	62,329
Fair value option | Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		58,094	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	1,921	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0
Purchases, issuances, sales and settlements
Purchases		0	0
Issuances		0	0
Sales		0	0
Settlements		0	0
Transfers in and/or out of Level 3		0	0
Balance at end of period		60,015	0
Equity securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period		55,889	0
Total gains or (losses) (realized/unrealized) - included in earnings	[1]	(3,721)	0
Total gains or (losses) (realized/unrealized) - included in other comprehensive income		0	0
Purchases, issuances, sales and settlements
Purchases		3,464	0
Issuances		0	0
Sales		0	0
Settlements		0	0
Transfers in and/or out of Level 3		0	0
Balance at end of period		$ 55,632	$ 0

[1] Gains or losses were included in net realized gains (losses).

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