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
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Life
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	$ 2,108,569		$ 1,989,586
Statutory net income (loss)	(7,084)	$ 3,263
Property & Casualty
Statutory Accounting Practices [Line Items]
Statutory capital and surplus	1,251,194		$ 1,183,913
Statutory net income (loss)	$ 38,120	$ 13,058