Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Investments, Owned, Federal Income Tax Note [Line Items]
Federal statutory rate		35.00%	35.00%	35.00%
Income tax expense (benefit)		$ 2,384,000	$ (1,005,000)	$ (4,718,000)
Decrease in tax reserve deductible temporary difference		(4,860,000)
Offsetting tax reserve deductible temporary difference against taxable income		$ 4,860,000
Tax reserve against taxable income amortization period		8 years
Valuation allowance for deferred tax assets		$ 78,697,000	154,440,000
Unrecognized income tax benefit, net		2,637,000	4,391,000	3,404,000
Unrecognized income tax benefit, gross		12,557,000	12,547,000
Permanent tax benefit			7,391,000
Operating loss carry forward		$ 554,553,000	627,860,000
Operating loss carry forward, expiration period		15 years
Alternative minimum tax credit carry forward		$ 4,216,000	4,216,000
Minimum tax credit carry forward		4,216,000
Minimum tax credit carry forward net of valuation allowance		3,937,000
Penalties expense related to federal income tax		0	0	0
Interest expense (income) related to federal income tax		316,000	74,000	86,000
Interest payable arising from income tax examinations		477,000	161,000
Contributions from (distributions to) capital to Transamerica Corporation		(47,465,000)	(13,381,000)	$ 68,492,000
Foreign
Investments, Owned, Federal Income Tax Note [Line Items]
Tax credit carry forward		$ 9,831,000	$ 9,776,000
Foreign tax credit carry forward, expiration date in year		10 years	10 years
Capital Loss Carry forward
Investments, Owned, Federal Income Tax Note [Line Items]
Tax credit carry forward		$ 0	$ 84,000
Capital loss tax credit carry forward, expiration date in year		5 years	5 years
Capital loss tax credit carry forward, expiration year		2018
Earliest Tax Year
Investments, Owned, Federal Income Tax Note [Line Items]
Company's tax year			2011
Operating loss carry forward, expiration year		2023
Latest Tax Year
Investments, Owned, Federal Income Tax Note [Line Items]
Company's tax year			2015
Operating loss carry forward, expiration year		2031
Latest Tax Year | Foreign
Investments, Owned, Federal Income Tax Note [Line Items]
Foreign tax credit carry forward, expiration year		2026
Scenario Plan
Investments, Owned, Federal Income Tax Note [Line Items]
Federal statutory rate	21.00%