Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Millions	6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
OPERATING ACTIVITIES
Net income	$ 539.7	$ 436.1
Adjustments to reconcile net income to net cash used in operating activities:
Depreciation and amortization	33.1	27.3
Amortization of discounts and fees	2.4	2.6
Stock based compensation expense	31.0	26.1
Equity in earnings of unconsolidated entities	(2.7)	0.0
Distributions of earnings of unconsolidated entities	0.2	0.0
Excess income tax benefit from employee stock awards	0.0	(8.7)
Deferred income taxes	145.0	24.1
Inventory and land option charges	33.8	14.5
Gain on sale of assets	(14.5)	0.0
Changes in operating assets and liabilities:
Increase in construction in progress and finished homes	(514.5)	(603.5)
Increase in residential land and lots – developed, under development, held for development and held for sale	(271.5)	(96.3)
Decrease (increase) in other assets	4.4	(29.9)
(Increase) decrease in mortgage loans held for sale	(70.7)	75.5
Decrease in accounts payable, accrued expenses and other liabilities	(14.5)	(3.5)
Net cash (used in) provided by operating activities	(98.8)	(135.7)
INVESTING ACTIVITIES
Expenditures for property and equipment	(79.0)	(57.5)
Proceeds from sale of assets	253.4	0.0
Increase in restricted cash	(38.9)	(8.9)
Investment in unconsolidated entities	(0.1)	0.0
Return of investment in unconsolidated entities	15.2	0.0
Net principal decrease of other mortgage loans and real estate owned	0.0	1.0
Purchases of debt securities collateralized by residential real estate	0.0	(3.9)
Payments related to business acquisitions, net of cash acquired	(158.1)	(4.1)
Net cash (used in) provided by investing activities	(7.5)	(73.4)
FINANCING ACTIVITIES
Proceeds from notes payable	1,913.6	0.0
Repayment of notes payable	(1,752.5)	(0.5)
Advances (payments) on mortgage repurchase facility, net	69.8	(54.0)
Proceeds from stock associated with certain employee benefit plans	32.7	24.7
Excess income tax benefit from employee stock awards	0.0	8.7
Cash paid for shares withheld for taxes	(10.3)	(5.1)
Cash dividends paid	(94.1)	(74.7)
Repurchases of common stock	(47.9)	0.0
Distributions to noncontrolling interests, net	(2.0)	0.0
Net cash (used in) provided by financing activities	109.3	(100.9)
INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	3.0	(310.0)
Cash and cash equivalents at beginning of period	1,007.8	1,303.2
Cash and cash equivalents at end of period	1,010.8	993.2
Supplemental disclosures of non-cash activities:
Notes payable issued for inventory	0.0	4.5
Stock issued under employee incentive plans	$ 63.4	31.7
Accounting Standards Update 2016-09 [Member]
FINANCING ACTIVITIES
Cash paid for shares withheld for taxes		$ (5.1)