Summary of Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 4,200	$ 4,300
Proceeds from sale/maturity of short-term investments	193,465	157,825	$ 192,994
Research and development	$ 113,215	$ 98,683	$ 101,950
Subsequent Event | ASU 606
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect upon adoption of new accounting principle, increase in retained earnings net of tax				$ 7,000
Common stock Warrants
Summary Of Significant Accounting Policies [Line Items]
Common stock warrants issued, per warrant	$ 26.68
SEC Rule 10b5-1 Plan
Summary Of Significant Accounting Policies [Line Items]
Repurchase of common stock, shares	0.5	0.3	0.3
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property and equipment, useful lives	3 years
Minimum | Cloud and Related Solutions Revenue
Summary Of Significant Accounting Policies [Line Items]
Long-term arrangements service period	3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Short-term investment contractual maturities	2 years	2 years
Property and equipment, useful lives	10 years
Maximum | Cloud and Related Solutions Revenue
Summary Of Significant Accounting Policies [Line Items]
Long-term arrangements service period	5 years