Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Domestic	$ 0		$ 0	$ 12,962
Gross unrecognized tax benefits	30,855		30,855	40,300	$ 30,554	$ 48,604
Unrecognized Tax Benefits that Would Impact Effective Tax Rate	24,400		24,400	21,600
Unrecognized tax benefits, income tax penalties and interest accrued	2,800		2,800	$ 6,500
Federal Energy Efficient Home Credit	24,000	$ 53,200	82,000
Home Closed in Prior Open Tax Year Benefit			$ 56,800
Maximum
Income Tax Contingency [Line Items]
IncomeTaxNetOperatingLossCarryforwardPeriod			20 years
2019 - 2023 [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	36,400		$ 36,400
2024 - Thereafter [Member] | State and Local Jurisdiction [Member]
Income Tax Contingency [Line Items]
Deferred Tax Assets, Operating Loss Carryforwards, Subject to Expiration	$ 147,600		$ 147,600