Revenue (Narrative - Performance Obligations) (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Sep. 30, 2019
Remaining performance obligation amount	$ 1,728,437	$ 1,527,437
Material Rights [Member]
Remaining performance obligation amount	454,471
Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-10-01
Remaining performance obligation amount	$ 4,666
Remaining performance obligation, expected timing of satisfaction, year	2020
Period of remaining performance obligation, expected timing of satisfaction	6 months
Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-10-01
Remaining performance obligation amount	$ 7,595
Remaining performance obligation, expected timing of satisfaction, year	2021
Period of remaining performance obligation, expected timing of satisfaction	1 year 6 months
Maximum [Member] | Material Rights [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Period of remaining performance obligation, expected timing of satisfaction	40 years
Aerospace [Member] | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Period of remaining performance obligation, expected timing of satisfaction	2 years