General form of registration statement for all companies including face-amount certificate companies

Stock-Based Compensation - Schedule of Unrecognized Compensation Cost, Nonvested Awards (Details)

v3.8.0.1
Stock-Based Compensation - Schedule of Unrecognized Compensation Cost, Nonvested Awards (Details) - Employee Stock Option [Member] - USD ($)
$ in Thousands
9 Months Ended 12 Months Ended
Sep. 30, 2017
Dec. 31, 2016
Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Unrecognized stock-based compensation $ 88 $ 256 $ 484
Weighted average remaining period of recognition (in years) 7 months 24 days 1 year 1 month 17 days 1 year 10 months 24 days