v3.8.0.1
Organization and Summary of Significant Accounting Policies (Tables)
 12 Months Ended
Dec. 31, 2017
Disclosure Organization And Summary Of Significant Accounting Policies Additional Information [Abstract]  
Schedule of Revenue from External Customers and Long-Lived Assets, by Geographical Areas [Table Text Block]
During fiscal years 2017, 2016 and 2015, total revenues attributable to the United States and outside of the United States were as follows (in millions, except percentages):
 
Years Ended December 31,
 
2017
 
2016
 
2015
 
Amount
 
%
of Total
 
Amount
 
%
of Total
 
Amount
 
%
of Total
Revenues:
 
 
 
 
 
 
 
 
 
 
 
United States
$
596.2

 
83
%
 
$
497.5

 
87
%
 
$
347.4

 
86
%
Outside of the United States
122.3

 
17
%
 
75.8

 
13
%
 
54.6

 
14
%
Total
$
718.5

 
100
%
 
$
573.3

 
100
%
 
$
402.0

 
100
%
Schedules of Concentration of Risk, by Risk Factor [Table Text Block]
The following table summarizes customers who accounted for 10% or more of net accounts receivable:
 
 
December 31,
 
 
2017
 
2016
Customer A
 
13%
 
22%
Customer B
 
19%
 
18%