Commitments and Contingencies Health Benefit Plan Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Commitments and Contingencies Disclosure [Abstract]
US Employee Group Health Insurance Expense	$ 6,096	$ 6,727	$ 21,592	$ 20,360