Debt (Premiums, Discounts and Debt Issuance Costs) (Details) - USD ($) $ in Thousands		1 Months Ended	6 Months Ended
	Mar. 31, 2016	Mar. 31, 2016	Sep. 30, 2017
Debt Disclosure [Abstract]
Non-cash expense for write-off of debt issuance costs on Senior Notes	$ 17,756
Non-cash expense for write-off of debt discount costs on Senior Notes	4,014
Non-cash gain for write-off of debt premium on Senior Notes	(4,800)
Total	$ 16,970	$ 16,970	$ 0