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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Life insurance entities
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 2,268,400		$ 2,268,400		$ 1,989,586
Statutory net income	26,498	$ 9,537	32,196	$ 25,650
Property and casualty insurance entities
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,295,544		1,295,544		$ 1,183,913
Statutory net income	$ 15,626	$ 21,382	$ 66,090	$ 30,611