Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015
Investments, Owned, Federal Income Tax Note [Line Items]
Federal statutory rate	35.00%		35.00%
Income tax expense (benefit)	$ 575		$ 0
Valuation allowance for deferred tax assets	145,235	$ 154,440		$ 154,440
Unrecognized income tax benefit, net	4,391	4,391		4,391	$ 3,404
Unrecognized income tax benefit, gross	12,547	12,547		12,547
Permanent tax benefit		7,391
Operating loss carry forward	$ 583,013	627,860		627,860
Operating loss carry forward, expiration period	15 years
Alternative minimum tax credit carry forward	$ 4,216	4,216		4,216
Penalties expense related to federal income tax	0		0
Interest expense (income) related to federal income tax	37		$ 45
Interest payable arising from income tax examinations	199	161		161
Return of capital to Transamerica Corporation	(13,400)			(13,381)
Foreign
Investments, Owned, Federal Income Tax Note [Line Items]
Tax credit carry forward	$ 9,943	9,776		$ 9,776
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	$ 84	$ 84		$ 84
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	2027