Stockholders' Equity and Noncontrolling Interests - Statutory Capital and Surplus and Net Income of Insurance Entities in Accordance with Statutory Accounting Practices (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Life insurance entities
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 2,146,806		$ 2,146,806		$ 1,989,586
Statutory net income (loss)	12,782	$ 12,850	5,698	$ 16,113
Property and casualty insurance entities
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,268,057		1,268,057		$ 1,183,913
Statutory net income (loss)	$ 12,344	$ (3,828)	$ 50,464	$ 9,230