Revenue (Narrative - Performance Obligations) (Details) $ in Thousands	Sep. 30, 2019 USD ($)
Remaining performance obligation amount	$ 1,527,437
Material Rights [Member]
Remaining performance obligation amount	424,773
Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Remaining performance obligation amount	$ 11,119
Remaining performance obligation, expected timing of satisfaction, year	2020
Period of remaining performance obligation, expected timing of satisfaction	1 year
Maximum [Member] | Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Period of remaining performance obligation, expected timing of satisfaction	40 years
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