Stockholder's Equity and Statutory Accounting Principles - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 51,392	$ (61,541)
Statutory capital and surplus	738,178		$ 696,073
Cash dividend paid	0	0
Return of capital to Transamerica Corporation /TA Corp	(13,400)		(13,381)
Additional Paid-in Capital
Statutory Accounting Practices [Line Items]
Return of capital to Transamerica Corporation /TA Corp	$ 13,440	$ 30,489	$ 88,341