Income Taxes (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended	9 Months Ended
	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2018	Mar. 31, 2017
Income Taxes
Federal, state and local income tax (benefit)/expense		$ (2,275)		$ 7,337		$ 23,286	$ (2,003)
Effective income tax rate (as a percent)		(21.70%)		33.00%		36.80%	24.20%
Federal income tax at statutory rate (as a percent)			21.00%		35.00%
Income tax charge, adjustment of deferred tax asset	$ 11,100	$ 8,100
Lower blended federal statutory tax rate (as a percent)			28.00%
Income tax benefit		$ (763)				$ (4,600)