Share Based Awards - Options activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Options Activity Rollforward
Number of Shares Available for Issuance, Beginning Balance	2,337,545	1,859,997	4,199,415
Number of Shares, Beginning Balance	4,496,557	7,738,496	9,835,992
Number of Shares Available for Issuance, Authorized	5,310,327	4,860,197	4,453,425
Number of Shares Available for Issuance, Granted	(125,000)	(400,000)	(300,000)
Options Outstanding, Shares Granted	125,000	400,000	300,000
Number of Shares Available for Issuance, other than Options granted			(9,329,181)
Options exercised	(1,349,694)	(2,488,544)	(1,172,409)
Number of Shares Available for Issuance, Cancelled	372,886	1,153,395	1,225,087
Number of Shares Available for Issuance, Ending Balance	1,301,881	2,337,545	1,859,997	4,199,415
Number of Shares, Ending Balance	2,898,977	4,496,557	7,738,496	9,835,992
Vested and exercisable- end of the period	2,410,434
Vested and expected to vest - end of the period	2,823,917
Options Activity, Weighted Average Exercise Price Rollforward
Options Outstanding, Weighted-Average Exercise Price, Beginning Balance	$ 5.02	$ 4.34	$ 4.39
Options Outstanding, Weighted Average Exercise Price Granted	4.52	4.71	4.20
Options Outstanding, Weighted Average Exercise Price Exercised	4.09	2.62	2.80
Options Outstanding, Weighted Average Exercise Price Cancelled	7.07	5.49	6.24
Options Outstanding, Weighted-Average Exercise Price, Ending Balance	5.17	$ 5.02	$ 4.34	$ 4.39
Options Outstanding, Weighted-Average Exercise Price, Vested and exercisable	5.32
Options Outstanding, Weighted-Average Exercise Price, Vested and expected to vest	$ 5.19
Options Outstanding, Weighted-Average Remaining Contractual Term (Years)	4 years 10 months 21 days	4 years 11 months 23 days	3 years 11 months 16 days	6 years 2 months 23 days
Options Outstanding, Weighted-Average Remaining Contractual Term Vested and exercisable (Years)	4 years 2 months 1 day
Options Outstanding, Weighted-Average Remaining Contractual Term Vested and expected to vest (Years)	4 years 9 months 15 days
Options Outstanding, Aggregate Intrinsic Value	$ 1,556	$ 2,446	$ 4,897	$ 5,734
Options Outstanding, Vested and exercisable, Aggregate Intrinsic Value	1,353
Options Outstanding, Vested and expected to vest, Aggregate Intrinsic Value	$ 1,530
RSUs, excluding Bonus Plans
Options Activity Rollforward
Number of Shares Available for Issuance, other than Options granted	(8,232,716)	(8,250,061)
Shares withheld for net settlement of equity awards (in shares)			677,547
Restricted stock units
Options Activity Rollforward
Number of Shares Available for Issuance, other than Options granted	(10,403,571)	(10,224,832)	(11,017,278)
Shares withheld for net settlement of equity awards (in shares)	1,147,904	1,294,360
Number of Shares Available for Issuance, Restricted stock units cancelled	2,661,790	3,794,428	2,621,801
2018 Bonus Plans
Options Activity Rollforward
Number of Shares Available for Issuance, other than Options granted	(2,170,855)
2017 Bonus Plans
Options Activity Rollforward
Number of Shares Available for Issuance, other than Options granted		(1,974,771)
2016 Bonus Plans
Options Activity Rollforward
Number of Shares Available for Issuance, other than Options granted			(1,688,097)