Insurance Activity - Components of Liability for Losses and Loss Adjustment Reserves (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016		Dec. 31, 2015
Effects of Reinsurance [Line Items]
Total losses and loss adjustment reserves	$ 688	$ 811	[1]	$ 5,063
Case-basis reserves [Member]
Effects of Reinsurance [Line Items]
Total losses and loss adjustment reserves	229	553
IBNR reserves [Member]
Effects of Reinsurance [Line Items]
Total losses and loss adjustment reserves	1
Premium deficiency reserves [Member]
Effects of Reinsurance [Line Items]
Total losses and loss adjustment reserves	$ 458	$ 258

[1] Balances derived from audited financial statements as of December 31, 2016.