Shareholders' Equity - Forward Sales Agreement (Details) $ / shares in Units, $ in Thousands	6 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Class of Stock [Line Items]
Shares Available (in shares) | shares	3,800,657
Net Proceeds Available | $	$ 418,580
June 30, 2019
Class of Stock [Line Items]
Shares Available (in shares) | shares	486,201
Net Proceeds Available | $	$ 48,819
Forward Price (dollars per share) | $ / shares	$ 100.41
September 30, 2019
Class of Stock [Line Items]
Shares Available (in shares) | shares	1,423,599
Net Proceeds Available | $	$ 153,426
Forward Price (dollars per share) | $ / shares	$ 107.77
December 31, 2019
Class of Stock [Line Items]
Shares Available (in shares) | shares	339,574
Net Proceeds Available | $	$ 36,218
Forward Price (dollars per share) | $ / shares	$ 106.66
March 31, 2020
Class of Stock [Line Items]
Shares Available (in shares) | shares	1,551,283
Net Proceeds Available | $	$ 180,117
Forward Price (dollars per share) | $ / shares	$ 116.11