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Income Taxes - Reconciliation of effective tax rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Expected income tax expense (benefit) computed on pre-tax income at weighted average income tax rate	$ 111,947	$ 149,799	$ 91,529
Addition (reduction) in income tax expense (benefit) resulting from:
Tax-exempt investment income	(1,824)	(3,091)	(4,790)
Meals and entertainment	547	1,134	1,060
State taxes, net of U.S. federal tax benefit	5,027	3,314	2,086
Foreign branch taxes	2,094	1,231	5,428
Prior year adjustment	3,983	632	(2,522)
Foreign exchange gains & losses	(1,736)	436	1,293
Changes in applicable tax rate	0	0	(128)
Dividend withholding taxes	7,105	6,510	6,594
Change in valuation allowance	13,190	1,628	18,396
Contingent consideration	9	190	740
Share based compensation	(2,533)	(6,592)	(5,356)
Effective Income Tax Reconciliation, Intercompany Loan Writeoff, Amount	(22,083)	0	0
Other	(3,888)	619	(379)
Income tax expense	$ 111,838	$ 155,810	$ 113,951

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The portion of the difference, between total income tax expense or benefit as reported in the Income Statement for the year/accounting period and the expected income tax expense or benefit computed by applying the domestic federal statutory income tax rates to pretax income from continuing operations, that is attributable to withholding taxes on dividends.

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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