Variable Interest Entity and Noncontrolling Interests - Variable interest entity (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2014	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Variable Interest Entity [Line Items]
Proceeds on issuance of preference shares			$ 0	$ 0	$ 319,694
Watford Holdings Ltd | Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Initial capitalization amount		$ 1,100,000
Proceeds from from common shares issued, net	$ 895,600
Proceeds on issuance of preference shares	219,200
Initial investment contribution amount	$ 100,000
Number of shares acquired	2,500,000	2,500,000
Number of shares called by warrants	975,503	975,503
Ownership percentage			13.00%
Watford Holdings Ltd | Variable Interest Entity, Primary Beneficiary | Common shares
Variable Interest Entity [Line Items]
Initial capitalization amount		$ 907,300
Watford Holdings Ltd | Variable Interest Entity, Primary Beneficiary | Preference equity
Variable Interest Entity [Line Items]
Initial capitalization amount		$ 226,600