Cash Flow Statement- Supplemental Information - Additional Information (Details)	6 Months Ended
	Jun. 30, 2017 USD ($)
Supplemental Cash Flow Information [Abstract]
Acquisition of net assets	$ 700
Deferred tax assets, net	22,200,000
Deferred tax liabilities, net	100,000
Deferred credits	21,400,000
Accounts receivable and unbilled, net	600,000
Other assets	$ 100,000