Shareholders' Equity - Schedule of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2021	Jun. 30, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 7,820,925	$ 7,213,156	$ 6,791,203	$ 6,304,415	$ 6,127,775	$ 5,750,223	$ 6,791,203	$ 5,750,223
Other comprehensive income (loss) before reclassifications							115,403	(4,730)
Amounts reclassified from accumulated other comprehensive income							3,425	2,586
Net current-period other comprehensive income (loss)	(79,232)	137,939	60,121	(4,086)	890	1,052	118,828	(2,144)
Shareholders' equity, ending balance	7,773,758	7,820,925	7,213,156	6,461,471	6,304,415	6,127,775	7,773,758	6,461,471
Available- for-Sale Securities
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance			238			132	238	132
Other comprehensive income (loss) before reclassifications							(165)	202
Amounts reclassified from accumulated other comprehensive income							0	(2)
Net current-period other comprehensive income (loss)							(165)	200
Shareholders' equity, ending balance	73			332			73	332
Interest Rate Agreement Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance			(57,827)			(114,715)	(57,827)	(114,715)
Other comprehensive income (loss) before reclassifications							115,568	(4,932)
Amounts reclassified from accumulated other comprehensive income							3,425	2,588
Net current-period other comprehensive income (loss)							118,993	(2,344)
Shareholders' equity, ending balance	61,166			(117,059)			61,166	(117,059)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	140,471	2,532	(57,589)	(112,641)	(113,531)	(114,583)	(57,589)	(114,583)
Net current-period other comprehensive income (loss)	(79,232)	137,939	60,121	(4,086)	890	1,052
Shareholders' equity, ending balance	$ 61,239	$ 140,471	$ 2,532	$ (116,727)	$ (112,641)	$ (113,531)	$ 61,239	$ (116,727)