Stock-Based Compensation - Option Plan (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Option Plan
Number of shares
Balance at beginning of year (in shares)	462,000	627,000	649,000
Granted (in shares)	0	0	0
Exercised (in shares)	(245,666)	(66,000)
Forfeited (in shares)		(99,000)	(22,000)
Balance at end of year (in shares)	216,334	462,000	627,000
Exercisable (in shares)	216,334
Weighted-Average Exercise Price
Balance at beginning of year (in dollars per share)	$ 0.0003	$ 0.0004	$ 0.0004
Exercised (in dollars per share)	0.0003	0.0005
Forfeited (in dollars per share)		0.0003	0.0001
Balance at end of year (in dollars per share)	0.0004	$ 0.0003	$ 0.0004
Exercisable at end of year (in dollars per share)	$ 0.0004
Weighted- Average Remaining Contractual Term (in Years)
Balance (in years)	5 years 4 months 2 days
Exercisable	5 years 4 months 2 days
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option life (in years)	10 years
Stock Options | Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option life (in years)	10 years
Weighted- Average Remaining Contractual Term (in Years)
Aggregate intrinsic value of stock option awards outstanding	$ 898