Income Taxes - Components of income tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Current expense (benefit):
United States	$ 139,407	$ 73,078	$ (51,705)
Non-U.S.	4,954	12,785	5,969
Current Income Tax Expense (Benefit)	144,361	85,863	(45,736)
Deferred expense (benefit):
United States	11,849	19,544	169,093
Non-U.S.	(400)	8,544	4,211
Deferred Income Tax Expense (Benefit)	11,449	28,088	173,304
Income tax expense (benefit)	$ 155,810	$ 113,951	$ 127,568