Stockholder's Equity and Statutory Accounting Principles - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Policyholders Account In Life Insurance Business [Abstract]
Statutory net income (loss)	$ 127,480	$ (20,821)
Statutory capital and surplus	822,000		$ 696,073
Cash dividend paid	0	75,000
Return of capital to Transamerica Corporation /TA Corp	$ 35,760	$ 5,762