Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Stock Repurchase Program, Authorized Amount							$ 1,000.0
Treasury Stock, Shares, Acquired		1,000,000.0
Payments for Repurchase of Common Stock		$ 69.8
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 465.5
Dividends, Common Stock [Abstract]
Divedends declared (in dollars per sh		$ 0.20	$ 0.175	$ 0.175	$ 0.175	$ 0.175
Cash dividends paid per common share (in dollars per share)		$ 0.20	$ 0.175	$ 0.175	$ 0.175	$ 0.175
Subsequent Event [Member]
Dividends, Common Stock [Abstract]
Divedends declared (in dollars per sh	$ 0.20
Forestar Group [Member]
Class of Stock [Line Items]
Equity Securities Registered, Value		$ 500.0
Dividends, Common Stock [Abstract]
Common Stock Available for Issuance, Value Remaining		$ 394.3
At-the-market Equity Offering Program, Common Stock Issued		0
At-the-market Equity Offering Program, Common Stock Available for Issuance		$ 100.0