Goodwill and Purchased Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Identifiable Intangible Assets [Abstract]
Goodwill, gross	$ 215,367	$ 215,367
Goodwill impairment charge	192,872	192,872
Goodwill	22,495	22,495
Amortization	1,534	$ 1,940	$ 2,320
Future amortization expense, next twelve month	1,548
Future amortization expense, 2020	1,346
Future amortization expense, 2021	598
Future amortization expense, 2022	532
Future amortization expense, 2023	$ 515