Revenue (Narrative - Performance Obligations) (Details) $ in Thousands	Jun. 30, 2019 USD ($)
Remaining performance obligation amount	$ 1,659,788
Material Rights [Member]
Remaining performance obligation amount	436,876
Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Remaining performance obligation amount	$ 2,253
Remaining performance obligation, expected timing of satisfaction, year	2019
Period of remaining performance obligation, expected timing of satisfaction	3 months
Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Remaining performance obligation amount	$ 11,573
Remaining performance obligation, expected timing of satisfaction, year	2020
Period of remaining performance obligation, expected timing of satisfaction	1 year 3 months
Aerospace [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Period of remaining performance obligation, expected timing of satisfaction	2 years