Variable Interest Entities and Noncontrolling Interests - Variable interest entity (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended
	Jul. 02, 2019	Mar. 31, 2014	Mar. 31, 2020	Mar. 31, 2019
Variable Interest Entity [Line Items]
Net cash used for operating activities			$ 610,454	$ 235,398
Net cash used for investing activities			(278,496)	(294,793)
Net cash provided by financing activities			$ (134,496)	41,519
Variable Interest Entity, Primary Beneficiary | Watford Holdings Ltd
Variable Interest Entity [Line Items]
Initial investment contribution amount		$ 100,000
Number of shares acquired		2,500,000
Ownership percentage		11.00%	13.00%
Senior notes, face amount	$ 175,000
Senior notes, stated percentage	6.50%
Proceeds from issuance of senior notes	$ 172,400
Senior notes acquired	$ 35,000
Net cash used for operating activities			$ 24,600	70,300
Net cash used for investing activities			(35,700)	(105,900)
Net cash provided by financing activities			$ 12,300	$ 28,100