Stockholder's Equity and Statutory Accounting Principles - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statutory Accounting Practices [Line Items]
Statutory net income (loss)	$ 193,953	$ 71,053	$ (24,119)
Statutory capital and surplus	731,065	696,073
Dividend distribution not require approval	226,423	142,822
Cash dividend paid	140,000	75,000
Capital contributions from AUSA			68,492
Additional Paid-in Capital
Statutory Accounting Practices [Line Items]
Return of capital to Transamerica Corporation /AEGON USA, LLC	$ 47,505	$ 88,341	$ 100,000