Significant Accounting Policies - Acquisition (Details) - USD ($) $ in Thousands	Aug. 01, 2021	Dec. 31, 2021	Dec. 31, 2020
Assets Acquired:
Goodwill		$ 481,791	$ 441,591
Beazley Insurance Company
Business Acquisition [Line Items]
Acquisition consideration	$ 59,200
Amount of coinsurance	100.00%
Assets Acquired:
Goodwill	$ 40,200
Assets acquired	56,700
Ceding commission	2,500
Total purchase price	59,200
Beazley Insurance Company | Trade name
Assets Acquired:
Intangible assets	300
Beazley Insurance Company | Customer relationships
Assets Acquired:
Intangible assets	5,200
Beazley Insurance Company | Distribution
Assets Acquired:
Intangible assets	$ 11,000