Fair Value Measurement (Details 2) - USD ($) $ in Millions | Dec. 31, 2015 | Sep. 30, 2015 | Dec. 31, 2014 | Sep. 30, 2014 |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Carrying value | | $ 1,268.7 | $ 1,383.8 | $ 541 | $ 661.8 |
Notes payable, Carrying value | | 3,734.3 | 3,811.5 | | |
Homebuilding [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Carrying value | | 1,245.7 | 1,355.9 | | |
Restricted cash, Carrying value | | 9.7 | 9.7 | | |
Notes payable, Carrying value | | 3,337.2 | 3,333.6 | | |
Homebuilding [Member] | Estimated Fair Value [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 1,245.7 | 1,355.9 | | |
Restricted cash, Fair value | [1] | 9.7 | 9.7 | | |
Homebuilding [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 1,245.7 | 1,355.9 | | |
Restricted cash, Fair value | [1] | 9.7 | 9.7 | | |
Homebuilding [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 0 | 0 | | |
Restricted cash, Fair value | [1] | 0 | 0 | | |
Homebuilding [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 0 | 0 | | |
Restricted cash, Fair value | [1] | 0 | 0 | | |
Financial Services [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Carrying value | | 23 | 27.9 | | |
Mortgage repurchase facility | | 397.1 | 477.9 | | |
Financial Services [Member] | Estimated Fair Value [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 23 | 27.9 | | |
Mortgage repurchase facility, Fair value | [1] | 397.1 | 477.9 | | |
Financial Services [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 23 | 27.9 | | |
Mortgage repurchase facility, Fair value | [1] | 0 | 0 | | |
Financial Services [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 0 | 0 | | |
Mortgage repurchase facility, Fair value | [1] | 0 | 0 | | |
Financial Services [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Cash and cash equivalents, Fair value | [1] | 0 | 0 | | |
Mortgage repurchase facility, Fair value | [1] | 397.1 | 477.9 | | |
Senior Notes [Member] | Homebuilding [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Carrying value | | 3,326.6 | 3,325.5 | | |
Senior Notes [Member] | Homebuilding [Member] | Estimated Fair Value [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 3,394.3 | 3,405.9 | | |
Senior Notes [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 0 | 0 | | |
Senior Notes [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 3,394.3 | 3,405.9 | | |
Senior Notes [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 0 | 0 | | |
Secured Debt [Member] | Homebuilding [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Carrying value | | 10.6 | 8.1 | | |
Secured Debt [Member] | Homebuilding [Member] | Estimated Fair Value [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 10.6 | 8.1 | | |
Secured Debt [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 1 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 0 | 0 | | |
Secured Debt [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 2 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | 0 | 0 | | |
Secured Debt [Member] | Homebuilding [Member] | Fair Value, Inputs, Level 3 [Member] | | | | | |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] | | | | | |
Notes payable, Fair value | [2] | $ 10.6 | $ 8.1 | | |
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[1] | The fair value approximates carrying value due to its short-term nature, short maturity or floating interest rate terms, as applicable. | |
[2] | The fair value is determined based on quoted market prices of recent transactions of the notes, which is classified as Level 2 within the fair value hierarchy. | |