Income Taxes - Income before taxes by jurisdiction (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Line Items]
Income (loss) before income taxes	$ 1,849,110	$ 841,772	$ 757,277
Bermuda
Income Tax Disclosure [Line Items]
Income (loss) before income taxes	1,122,952	388,492	406,054
United States
Income Tax Disclosure [Line Items]
Income (loss) before income taxes	701,480	440,823	381,157
Other
Income Tax Disclosure [Line Items]
Income (loss) before income taxes	$ 24,678	$ 12,457	$ (29,934)