Summary of Significant Accounting Policies - Property Plant and Equipment (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Year	Dec. 31, 2016 USD ($)
Property, Plant and Equipment [Line Items]
Unamortized software development costs | $	$ 535,203	$ 477,670
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Minimum Useful Life	20
Property, Plant and Equipment, Maximum Useful Life	30
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Minimum Useful Life	3
Property, Plant and Equipment, Maximum Useful Life	10
Computer Software, Intangible Asset [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Minimum Useful Life	3
Property, Plant and Equipment, Maximum Useful Life	12