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Debt - Schedule of Carrying Value of Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2020	May 19, 2020	May 15, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Total	$ 2,077,991			$ 2,274,990
Convertible Debt
Debt Instrument [Line Items]
Convertible senior notes	$ 1,845,594			1,553,039
Convertible Debt \| 1.375% convertible senior notes due 2026
Debt Instrument [Line Items]
Stated Interest Rate	1.375%
Convertible senior notes	$ 342,316			327,187
Convertible Debt \| 2.75% convertible senior notes due 2025
Debt Instrument [Line Items]
Stated Interest Rate	2.75%	2.75%	2.75%
Convertible senior notes	$ 408,323			0
Convertible Debt \| 0.75% convertible senior notes due 2024
Debt Instrument [Line Items]
Stated Interest Rate	0.75%
Convertible senior notes	$ 515,573			490,538
Convertible Debt \| 1.50% convertible senior notes due 2023
Debt Instrument [Line Items]
Stated Interest Rate	1.50%
Convertible senior notes	$ 322,535			310,175
Convertible Debt \| 2.00% convertible senior notes due 2021
Debt Instrument [Line Items]
Stated Interest Rate	2.00%
Convertible senior notes	$ 249,263			415,502
Convertible Debt \| 2.75% convertible senior notes due 2020
Debt Instrument [Line Items]
Stated Interest Rate	2.75%
Convertible senior notes	$ 7,584			9,637
Mortgages Segment
Debt Instrument [Line Items]
Warehouse line of credit	118,094			30,427
Line of Credit \| Homes Segment
Debt Instrument [Line Items]
Short-term debt	114,303			691,524
Goldman Sachs Bank USA \| Line of Credit \| Homes Segment
Debt Instrument [Line Items]
Short-term debt	22,460			39,244
Citibank, N.A. \| Mortgages Segment
Debt Instrument [Line Items]
Short-term debt	58,859			394
Citibank, N.A. \| Line of Credit \| Homes Segment
Debt Instrument [Line Items]
Short-term debt	28,512			296,369
Credit Suisse AG, Cayman Islands \| Line of Credit \| Homes Segment
Debt Instrument [Line Items]
Short-term debt	63,331			355,911
Comerica Bank \| Line of Credit \| Mortgages Segment
Debt Instrument [Line Items]
Warehouse line of credit	$ 59,235			$ 30,033