Other Operating Expenses and Other Expenses - Summary of Other Operating Expenses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Other Operating Expenses And Other Expenses [Abstract]
Amortization of policy acquisition costs	$ 83,893	$ 111,103	$ 116,001
Other underwriting expenses of the insurance segments	59,351	63,029	55,662
Other operating expenses of the Corporate and Other segment	27,664	26,903	25,330
Total	$ 170,908	$ 201,035	$ 196,993