Shareholders' Equity - Schedule of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2021	Mar. 31, 2020
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	$ 7,213,156	$ 6,791,203	$ 6,127,775	$ 5,750,223	$ 6,791,203	$ 5,750,223
Other comprehensive income (loss) before reclassifications					195,777	(163)
Amounts reclassified from accumulated other comprehensive income					2,283	2,105
Net current-period other comprehensive income (loss)	137,939	60,121	890	1,052	198,060	1,942
Shareholders' equity, ending balance	7,820,925	7,213,156	6,304,415	6,127,775	7,820,925	6,304,415
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					(129)	(163)
Amounts reclassified from accumulated other comprehensive income					0	(1)
Net current-period other comprehensive income (loss)					(129)	(164)
Shareholders' equity, ending balance	109		(32)		109	(32)
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					195,906	0
Amounts reclassified from accumulated other comprehensive income					2,283	2,106
Net current-period other comprehensive income (loss)					198,189	2,106
Shareholders' equity, ending balance	140,362		(112,609)		140,362	(112,609)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Shareholders' equity, beginning balance	2,532	(57,589)	(113,531)	(114,583)	(57,589)	(114,583)
Net current-period other comprehensive income (loss)	137,939	60,121	890	1,052
Shareholders' equity, ending balance	$ 140,471	$ 2,532	$ (112,641)	$ (113,531)	$ 140,471	$ (112,641)