CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) - USD ($) $ in Thousands		3 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net income		$ 34,929	$ 50,282
Other comprehensive income, net of tax
Unrealized gain on available for sale securities, net of tax of $(3,786) and $(2,614), respectively		5,515	3,701
Net unrealized (loss) on derivatives, net of tax of $0 and $19, respectively	[1]	0	(33)
Adjustment to postemployment benefit obligation, net of tax of $(217) and $(174), respectively		317	256
Other comprehensive income		5,832	3,924
Comprehensive income		$ 40,761	$ 54,206

[1] Effective January 1, 2016, the Company elected not to designate its foreign currency derivatives as accounting hedges and, as a result, changes in fair value of the effective portion of the hedges are no longer recorded in OCI. See Note 4 Derivative Instruments for more information on these transactions.