CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 123,699	$ 34,929
Other comprehensive (loss) income, net of tax
Unrealized (loss) gain on available for sale securities, net of tax of $851 and $(3,786), respectively	(2,290)	5,515
Reclassifications of (gains) to net income on available for sale securities, net of tax of $2,178 and $0, respectively	(3,154)	0
Adjustment to postemployment benefit obligation, net of tax of $(136) and $(217), respectively	240	317
Other comprehensive (loss) income	(5,204)	5,832
Comprehensive income	$ 118,495	$ 40,761