Segment Information (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended | | |
Jun. 30, 2019 | Jun. 30, 2018 | Jun. 30, 2019 | Jun. 30, 2018 | Dec. 31, 2018 | Sep. 30, 2018 |
Segment Reporting Information [Line Items] | | | | | | |
Document Period End Date | | | Jun. 30, 2019 | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | $ 864.2 | | $ 864.2 | | | $ 1,473.1 |
Restricted cash | 21.1 | | 21.1 | | | 32.9 |
Inventories: | | | | | | |
Construction in progress and finished homes | 5,722.6 | | 5,722.6 | | | 5,086.3 |
Residential land and lots — developed and under development | 5,811.4 | | 5,811.4 | | | 5,172.4 |
Land held for development | 125.7 | | 125.7 | | | 96.1 |
Land held for sale | 42.6 | | 42.6 | | | 40.2 |
Total inventories | 11,702.3 | | 11,702.3 | | | 10,395 |
Mortgage loans held for sale | 954.9 | | 954.9 | | | 796.4 |
Deferred income taxes, net | 173.9 | | 173.9 | | | 194 |
Property and equipment, net | 454.2 | | 454.2 | | | 401.1 |
Other Assets | 889.9 | | 889.9 | | | 712.9 |
Goodwill | 163.5 | | 163.5 | | | 109.2 |
Total assets | 15,224 | | 15,224 | | | 14,114.6 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 681.2 | | 681.2 | | | 624.7 |
Accrued expenses and other liabilities | 1,277.5 | | 1,277.5 | | | 1,127.5 |
Notes payable | 3,450.6 | | 3,450.6 | | | 3,203.5 |
Total liabilities | 5,409.3 | | 5,409.3 | | | 4,955.7 |
Revenues | | | | | | |
Total revenues | 4,906.3 | $ 4,435.3 | 12,554 | $ 11,562.9 | | |
Cost of Goods and Services Sold | 3,831.6 | 3,397.2 | 9,839.4 | 8,939 | | |
Inventory and land option charges | 19.2 | 8.9 | 41 | 42.8 | | |
Cost of sales | 3,831.6 | 3,397.2 | 9,839.4 | 8,939 | | |
Selling, General and Administrative Expense | 480 | 434.9 | 1,327 | 1,219.9 | | |
Gain on sale of assets | (22.6) | 0 | (53.9) | (14.5) | | |
Interest Expense | | 0 | | 0 | | |
Other (income) expense | (9.4) | (13) | (23.7) | (33.8) | | |
Income (loss) before income taxes | 626.7 | 616.2 | 1,465.2 | 1,452.3 | | |
Depreciation and amortization | | | 52.4 | 46.6 | | |
Net cash provided by (used in) operating activities | | | 80.7 | 306.5 | | |
Segment Reconciling Items [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 0 | | 0 | | | 0 |
Restricted cash | 0 | | 0 | | | 0 |
Inventories: | | | | | | |
Construction in progress and finished homes | 0 | | 0 | | | 0 |
Residential land and lots — developed and under development | 2.9 | | 2.9 | | | 27.2 |
Land held for development | 0 | | 0 | | | 0 |
Land held for sale | 0 | | 0 | | | 0 |
Total inventories | 2.9 | | 2.9 | | | 27.2 |
Mortgage loans held for sale | 0 | | 0 | | | 0 |
Deferred income taxes, net | (5.2) | | (5.2) | | | (10.5) |
Property and equipment, net | 0 | | 0 | | | 0 |
Other Assets | 11.7 | | 11.7 | | | 11.9 |
Goodwill | 29.2 | | 29.2 | | | 29.2 |
Total assets | 38.6 | | 38.6 | | | 57.8 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 0 | | 0 | | | 0 |
Accrued expenses and other liabilities | (12.7) | | (12.7) | | | (15.2) |
Notes payable | 3.9 | | 3.9 | | | 8.2 |
Total liabilities | (8.8) | | (8.8) | | | (7) |
Revenues | | | | | | |
Total revenues | 0 | (1.2) | 0 | (1.2) | | |
Inventory and land option charges | 0 | 0 | 0 | 0 | | |
Cost of sales | 8.2 | 5.7 | 20 | 12.6 | | |
Selling, General and Administrative Expense | 0.1 | 0.1 | 0.3 | 0.3 | | |
Gain on sale of assets | 1.5 | 1.3 | 2.4 | 2.9 | | |
Interest Expense | | 0 | | 0 | | |
Other (income) expense | 0 | 1.3 | 0 | 7.7 | | |
Income (loss) before income taxes | (9.8) | (9.6) | (22.7) | (24.7) | | |
Depreciation and amortization | | | 0.4 | 0.4 | | |
Net cash provided by (used in) operating activities | | | (4.4) | (8.1) | | |
Intersegment Eliminations [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 0 | | 0 | | | 0 |
Restricted cash | 0 | | 0 | | | 0 |
Inventories: | | | | | | |
Construction in progress and finished homes | (0.9) | | (0.9) | | | 1.9 |
Residential land and lots — developed and under development | (27.6) | | (27.6) | | | (7.2) |
Land held for development | 0 | | 0 | | | 0 |
Land held for sale | 0 | | 0 | | | 0 |
Total inventories | (28.5) | | (28.5) | | | (5.3) |
Mortgage loans held for sale | 0 | | 0 | | | 0 |
Deferred income taxes, net | 3.7 | | 3.7 | | | 1.1 |
Property and equipment, net | 0 | | 0 | | | 0 |
Other Assets | (83) | | (83) | | | (48.6) |
Goodwill | 0 | | 0 | | | 0 |
Total assets | (107.8) | | (107.8) | | | (52.8) |
Liabilities [Abstract] | | | | | | |
Accounts payable | (0.7) | | (0.7) | | | (3.3) |
Accrued expenses and other liabilities | (93.7) | | (93.7) | | | (46.1) |
Notes payable | 0 | | 0 | | | 0 |
Total liabilities | (94.4) | | (94.4) | | | (49.4) |
Revenues | | | | | | |
Total revenues | (73.2) | (8.8) | (141.8) | (17.3) | | |
Inventory and land option charges | 0 | 0 | 0 | 0 | | |
Cost of sales | (67.3) | (5.6) | (125.3) | (12.3) | | |
Selling, General and Administrative Expense | 0 | 0 | 0 | 0 | | |
Gain on sale of assets | 0 | 0 | 0 | 0 | | |
Interest Expense | | (1.6) | | (5.8) | | |
Other (income) expense | 0 | 0 | 0 | 0 | | |
Income (loss) before income taxes | (5.9) | (1.6) | (16.5) | 0.8 | | |
Depreciation and amortization | | | 0 | 0 | | |
Net cash provided by (used in) operating activities | | | (2.5) | 0 | | |
Financial Service [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 44.7 | | 44.7 | | | 33.7 |
Restricted cash | 11.1 | | 11.1 | | | 8.1 |
Inventories: | | | | | | |
Construction in progress and finished homes | 0 | | 0 | | | 0 |
Residential land and lots — developed and under development | 0 | | 0 | | | 0 |
Land held for development | 0 | | 0 | | | 0 |
Land held for sale | 0 | | 0 | | | 0 |
Total inventories | 0 | | 0 | | | 0 |
Mortgage loans held for sale | 954.9 | | 954.9 | | | 796.4 |
Deferred income taxes, net | 0 | | 0 | | | 0 |
Property and equipment, net | 3.2 | | 3.2 | | | 3 |
Other Assets | 67.7 | | 67.7 | | | 43.6 |
Goodwill | 0 | | 0 | | | 0 |
Total assets | 1,081.6 | | 1,081.6 | | | 884.8 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 18.4 | | 18.4 | | | 0.2 |
Accrued expenses and other liabilities | 56.9 | | 56.9 | | | 41.9 |
Notes payable | 796.5 | | 796.5 | | | 637.7 |
Total liabilities | 871.8 | | 871.8 | | | 679.8 |
Revenues | | | | | | |
Total revenues | 119.6 | 97.1 | 306.4 | 273.1 | | |
Inventory and land option charges | 0 | 0 | 0 | 0 | | |
Cost of sales | 0 | 0 | 0 | 0 | | |
Selling, General and Administrative Expense | 76.4 | 71.1 | 213.4 | 199.6 | | |
Gain on sale of assets | 0 | 0 | 0 | 0 | | |
Interest Expense | | 0 | | 0 | | |
Other (income) expense | (4.9) | (4.3) | (12.6) | (10.5) | | |
Income (loss) before income taxes | 48.1 | 30.3 | 105.6 | 84 | | |
Depreciation and amortization | | | 1.1 | 1 | | |
Net cash provided by (used in) operating activities | | | (65.5) | (27) | | |
Home Building [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 577.9 | | 577.9 | | | 1,111.8 |
Restricted cash | 9.8 | | 9.8 | | | 8.6 |
Inventories: | | | | | | |
Construction in progress and finished homes | 5,723.5 | | 5,723.5 | | | 5,084.4 |
Residential land and lots — developed and under development | 4,847.4 | | 4,847.4 | | | 4,689.3 |
Land held for development | 64.9 | | 64.9 | | | 61.2 |
Land held for sale | 42.6 | | 42.6 | | | 40.2 |
Total inventories | 10,678.4 | | 10,678.4 | | | 9,875.1 |
Mortgage loans held for sale | 0 | | 0 | | | 0 |
Deferred income taxes, net | 154.4 | | 154.4 | | | 176.5 |
Property and equipment, net | 234.2 | | 234.2 | | | 207.1 |
Other Assets | 824.2 | | 824.2 | | | 673.7 |
Goodwill | 134.3 | | 134.3 | | | 80 |
Total assets | 12,613.2 | | 12,613.2 | | | 12,132.8 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 640.6 | | 640.6 | | | 612.4 |
Accrued expenses and other liabilities | 1,155.8 | | 1,155.8 | | | 1,041.3 |
Notes payable | 2,191.3 | | 2,191.3 | | | 2,445.9 |
Total liabilities | 3,987.7 | | 3,987.7 | | | 4,099.6 |
Revenues | | | | | | |
Total revenues | 4,762.1 | 4,324.6 | 12,175 | 11,231.3 | | |
Inventory and land option charges | 19.2 | 8.9 | 41 | 42.8 | | |
Cost of sales | 3,815.4 | 3,387.1 | 9,795.1 | 8,893.2 | | |
Selling, General and Administrative Expense | 387.4 | 349.1 | 1,071.4 | 976.6 | | |
Gain on sale of assets | 0 | 0 | (2) | (13.4) | | |
Interest Expense | | 0 | | 0 | | |
Other (income) expense | (2.5) | (1.3) | (6.1) | (4.6) | | |
Income (loss) before income taxes | 561.8 | 589.7 | 1,316.6 | 1,379.5 | | |
Depreciation and amortization | | | 46.4 | 39.8 | | |
Net cash provided by (used in) operating activities | | | 605.7 | 565.2 | | |
Forestar Group [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 223 | | 223 | | | 318.8 |
Restricted cash | 0.2 | | 0.2 | | | 16.2 |
Inventories: | | | | | | |
Construction in progress and finished homes | 0 | | 0 | | | 0 |
Residential land and lots — developed and under development | 988.7 | | 988.7 | | | 463.1 |
Land held for development | 60.8 | | 60.8 | | | 34.9 |
Land held for sale | 0 | | 0 | | | 0 |
Total inventories | 1,049.5 | | 1,049.5 | | | 498 |
Mortgage loans held for sale | 0 | | 0 | | | 0 |
Deferred income taxes, net | 21 | | 21 | | | 26.9 |
Property and equipment, net | 2.4 | | 2.4 | | | 1.8 |
Other Assets | 29.1 | | 29.1 | | | 31.4 |
Goodwill | 0 | | 0 | | | 0 |
Total assets | 1,325.2 | | 1,325.2 | | | 893.1 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 19.5 | | 19.5 | | | 11.2 |
Accrued expenses and other liabilities | 151.5 | | 151.5 | | | 95.7 |
Notes payable | 458.9 | | 458.9 | | | 111.7 |
Total liabilities | 629.9 | | 629.9 | | | 218.6 |
Revenues | | | | | | |
Total revenues | 88.2 | 23.6 | 192 | 77 | | |
Inventory and land option charges | 0 | 0 | 0 | 0 | | |
Cost of sales | 75.3 | 10 | 149.6 | 45.5 | | |
Selling, General and Administrative Expense | 7.9 | 6.5 | 19.8 | 25.6 | | |
Gain on sale of assets | (1.5) | (1.3) | (2.4) | (4) | | |
Interest Expense | | 1.6 | | 5.8 | | |
Other (income) expense | (1.9) | (3.7) | (4.6) | (15) | | |
Income (loss) before income taxes | 8.4 | 10.5 | 29.6 | 19.1 | | |
Depreciation and amortization | | | 0.2 | 0.2 | | |
Net cash provided by (used in) operating activities | | | (450.1) | (219.2) | | |
Other Segments [Member] | | | | | | |
Assets [Abstract] | | | | | | |
Cash and cash equivalents | 18.6 | | 18.6 | | | 8.8 |
Restricted cash | 0 | | 0 | | | 0 |
Inventories: | | | | | | |
Construction in progress and finished homes | 0 | | 0 | | | 0 |
Residential land and lots — developed and under development | 0 | | 0 | | | 0 |
Land held for development | 0 | | 0 | | | 0 |
Land held for sale | 0 | | 0 | | | 0 |
Total inventories | 0 | | 0 | | | 0 |
Mortgage loans held for sale | 0 | | 0 | | | 0 |
Deferred income taxes, net | 0 | | 0 | | | 0 |
Property and equipment, net | 214.4 | | 214.4 | | | 189.2 |
Other Assets | 40.2 | | 40.2 | | | 0.9 |
Goodwill | 0 | | 0 | | | 0 |
Total assets | 273.2 | | 273.2 | | | 198.9 |
Liabilities [Abstract] | | | | | | |
Accounts payable | 3.4 | | 3.4 | | | 4.2 |
Accrued expenses and other liabilities | 19.7 | | 19.7 | | | 9.9 |
Notes payable | 0 | | 0 | | | 0 |
Total liabilities | 23.1 | | 23.1 | | | 14.1 |
Revenues | | | | | | |
Total revenues | 9.6 | 0 | 22.4 | 0 | | |
Inventory and land option charges | 0 | 0 | 0 | 0 | | |
Cost of sales | 0 | 0 | 0 | 0 | | |
Selling, General and Administrative Expense | 8.2 | 8.1 | 22.1 | 17.8 | | |
Gain on sale of assets | (22.6) | 0 | (51.9) | 0 | | |
Interest Expense | | 0 | | 0 | | |
Other (income) expense | (0.1) | (5) | (0.4) | (11.4) | | |
Income (loss) before income taxes | 24.1 | (3.1) | 52.6 | (6.4) | | |
Depreciation and amortization | | | 4.3 | 5.2 | | |
Net cash provided by (used in) operating activities | | | (2.5) | (4.4) | | |
East [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 1,300.8 | | 1,300.8 | | | 1,192 |
Goodwill | | | | | $ 4.6 | |
Revenues | | | | | | |
Total revenues | 675.2 | 529.1 | 1,640.9 | 1,357.9 | | |
Inventory and land option charges | 0.6 | 0.3 | 2.3 | 0.9 | | |
Income (loss) before income taxes | 74.1 | 67.1 | 158 | 158.7 | | |
Midwest [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 818.5 | | 818.5 | | | 583.1 |
Goodwill | | | | | $ 49.7 | |
Revenues | | | | | | |
Total revenues | 303.3 | 256.7 | 800.5 | 621.7 | | |
Inventory and land option charges | 1.3 | 4.3 | 1.8 | 4.7 | | |
Income (loss) before income taxes | 18.7 | 23 | 38.8 | 55 | | |
Southeast [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 2,733.1 | | 2,733.1 | | | 2,668.7 |
Revenues | | | | | | |
Total revenues | 1,388.1 | 1,263.3 | 3,607.2 | 3,293.9 | | |
Inventory and land option charges | 5.1 | 1.1 | 8.6 | 27.3 | | |
Income (loss) before income taxes | 168.4 | 156.1 | 411.6 | 374.9 | | |
South Central [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 2,660.5 | | 2,660.5 | | | 2,439.4 |
Revenues | | | | | | |
Total revenues | 1,178 | 1,005.4 | 3,040.8 | 2,733.2 | | |
Inventory and land option charges | 3 | 1.5 | 4.9 | 3.5 | | |
Income (loss) before income taxes | 164.3 | 143.3 | 389.6 | 365.2 | | |
Southwest [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 606.2 | | 606.2 | | | 499.7 |
Revenues | | | | | | |
Total revenues | 240.6 | 220.1 | 557.5 | 548.6 | | |
Inventory and land option charges | 0.3 | 0 | 0.5 | 0.8 | | |
Income (loss) before income taxes | 33.5 | 32.3 | 69.8 | 69.1 | | |
West [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 2,325.7 | | 2,325.7 | | | 2,268.5 |
Revenues | | | | | | |
Total revenues | 976.9 | 1,050 | 2,528.1 | 2,676 | | |
Inventory and land option charges | 8.9 | 1.7 | 22.9 | 5.6 | | |
Income (loss) before income taxes | 102.8 | 167.9 | 248.8 | 356.6 | | |
Corporate, Non-Segment [Member] | Home Building [Member] | | | | | | |
Inventories: | | | | | | |
Total inventories | 233.6 | | 233.6 | | | $ 223.7 |
Land [Member] | | | | | | |
Revenues | | | | | | |
Sales | 52.1 | 72.7 | 121.8 | 167.7 | | |
Cost of Goods and Services Sold | 40.7 | 55.5 | 85 | 134.5 | | |
Land [Member] | Segment Reconciling Items [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | (1.2) | 0 | (1.2) | | |
Cost of Goods and Services Sold | 8.2 | 5.7 | 20 | 12.6 | | |
Land [Member] | Intersegment Eliminations [Member] | | | | | | |
Revenues | | | | | | |
Sales | (73.2) | (8.8) | (141.8) | (17.3) | | |
Cost of Goods and Services Sold | (66) | (5.6) | (122.2) | (12.3) | | |
Land [Member] | Financial Service [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Land [Member] | Home Building [Member] | | | | | | |
Revenues | | | | | | |
Sales | 27.5 | 59.1 | 49.2 | 109.2 | | |
Cost of Goods and Services Sold | 23.2 | 45.4 | 37.6 | 88.7 | | |
Land [Member] | Forestar Group [Member] | | | | | | |
Revenues | | | | | | |
Sales | 88.2 | 23.6 | 192 | 77 | | |
Cost of Goods and Services Sold | 75.3 | 10 | 149.6 | 45.5 | | |
Land [Member] | Other Segments [Member] | | | | | | |
Revenues | | | | | | |
Sales | 9.6 | 0 | 22.4 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Sales [Member] | | | | | | |
Revenues | | | | | | |
Sales | 4,734.6 | 4,265.5 | 12,125.8 | 11,122.1 | | |
Cost of Goods and Services Sold | 3,771.7 | 3,332.8 | 9,713.4 | 8,761.7 | | |
Sales [Member] | Segment Reconciling Items [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Sales [Member] | Intersegment Eliminations [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | (1.3) | 0 | (3.1) | 0 | | |
Sales [Member] | Financial Service [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Sales [Member] | Home Building [Member] | | | | | | |
Revenues | | | | | | |
Sales | 4,734.6 | 4,265.5 | 12,125.8 | 11,122.1 | | |
Cost of Goods and Services Sold | 3,773 | 3,332.8 | 9,716.5 | 8,761.7 | | |
Sales [Member] | Forestar Group [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Sales [Member] | Other Segments [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Cost of Goods and Services Sold | 0 | 0 | 0 | 0 | | |
Financial Service [Member] | | | | | | |
Revenues | | | | | | |
Sales | 119.6 | 97.1 | 306.4 | 273.1 | | |
Financial Service [Member] | Segment Reconciling Items [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Financial Service [Member] | Intersegment Eliminations [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Financial Service [Member] | Financial Service [Member] | | | | | | |
Revenues | | | | | | |
Sales | 119.6 | 97.1 | 306.4 | 273.1 | | |
Financial Service [Member] | Home Building [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Financial Service [Member] | Forestar Group [Member] | | | | | | |
Revenues | | | | | | |
Sales | 0 | 0 | 0 | 0 | | |
Financial Service [Member] | Other Segments [Member] | | | | | | |
Revenues | | | | | | |
Sales | $ 0 | $ 0 | $ 0 | $ 0 | | |