Stockholders' Equity (Changes in Nonvested Stock Options) (Details) - $ / shares shares in Thousands	3 Months Ended	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2018
Stock-Based Compensation
Number of Options, beginning balance	2,020	2,072
Weighted-Average Grant Date Fair Value Per Share, beginning balance	$ 21.63	$ 18.61
Options granted, Number of options	6	750
Options granted, Weighted-Average Grant Date Fair Value Per Share	$ 22.82	$ 25.66
Options vested, Number of options	(4)	(791)
Options vested, Weighted-Average Grant Date Fair Value Per Share	$ 23.10	$ 17.57
Options forfeited, Number of options	0	(9)
Options forfeited, Weighted-Average Grant Date Fair Value Per Share	$ 0.00	$ 19.82
Number of Options, ending balance	2,022	2,022
Weighted-Average Grant Date Fair Value Per Share, ending balance	$ 21.63	$ 21.63