Contracts and Revenue Recognition Change in Estimates on Long Term Contracts (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		15 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Sep. 30, 2018
Changes in Estimates on Long Term Contracts [Abstract]
Liquidated Damages on European Renewable Loss Contracts	$ 16,700				$ 49,600
Correction to changes in estimated future development costs		$ 6,200	$ 4,900
Operating Income	4,982			$ 12,019	14,182	$ 26,193
Operating loss	121,217			$ 38,839	124,588	$ 44,812
Change in construction cost estimates	$ (115,200)		$ (98,100)		$ (112,200)		$ 4,000