Summary of Significant Accounting Policies (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Fair value measurements
Amount of transfers between levels within the fair value hierarchy	$ 0	$ 0
Research and Development
Research and development expenses	7,137,000	7,705,000
Capitalized Software Costs
Expenditures for externally marketed software	(7,148,000)	(10,832,000)
Other noncurrent assets, net
Capitalized Software Costs
Net carrying amount of externally marketed software	89,700,000		$ 88,100,000
Externally marketed software under development and not yet placed in service	22,300,000		19,600,000
Expenditures for externally marketed software	(7,100,000)	(10,800,000)
Amortization expense relating to the development of externally marketed software	$ 5,500,000	3,400,000
Maximum
Capitalized Software Costs
Software useful life	5 years
Weighted Average
Capitalized Software Costs
Software useful life	4 years
Cost of Sales
Research and Development
Research and development expenses	$ 6,600,000	6,900,000
Research and Development Expense
Research and Development
Research and development expenses	7,100,000	$ 7,700,000
Level 2
Fair value measurements
Orbital incentive obligations	110,900,000		$ 112,200,000
Contract Acquisition Costs [Member]
Capitalized Contract Cost [Abstract]
Capitalized Contract Cost, Net	103,600,000
Capitalized Contract Cost, Amortization	20,000,000.0
Contract Fulfillment Costs [Member]
Capitalized Contract Cost [Abstract]
Capitalized Contract Cost, Net	$ 1,800,000