Debt and Credit Facilities (Details) (USD $)	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 5.4 percent senior notes due January 2015	Dec. 31, 2013 5.4 percent senior notes due January 2015	Mar. 31, 2014 8.4 percent senior notes due May 2017	Dec. 31, 2013 8.4 percent senior notes due May 2017	Mar. 31, 2014 6.6 percent senior notes due May 2020	Dec. 31, 2013 6.6 percent senior notes due May 2020	Mar. 31, 2014 5.4 percent senior notes due October 2022	Dec. 31, 2013 5.4 percent senior notes due October 2022	Mar. 31, 2014 1.6 percent convertible senior notes due May 2018	Dec. 31, 2013 1.6 percent convertible senior notes due May 2018	Mar. 31, 2014 0.25 percent convertible senior notes due June 2019	Dec. 31, 2013 0.25 percent convertible senior notes due June 2019	Mar. 31, 2014 Seller-financed nonrecourse secured notes	Dec. 31, 2013 Seller-financed nonrecourse secured notes	Mar. 31, 2014 Repurchase credit facility JPMorgan Chase Bank, N.A. ("JPM")	Dec. 31, 2013 Repurchase credit facility JPMorgan Chase Bank, N.A. ("JPM")	Dec. 31, 2011 Repurchase credit facility JPMorgan Chase Bank, N.A. ("JPM")	Apr. 30, 2014 Warehouse line of credit Comerica Bank Subsequent event RMCMC
Debt
Total senior notes and convertible senior notes	$ 1,398,981,000	$ 1,398,981,000	$ 126,481,000	$ 126,481,000	$ 230,000,000	$ 230,000,000	$ 300,000,000	$ 300,000,000	$ 250,000,000	$ 250,000,000	$ 225,000,000	$ 225,000,000	$ 267,500,000	$ 267,500,000
Debt discount	(2,195,000)	(2,362,000)
Senior notes and convertible senior notes, net	1,396,786,000	1,396,619,000
Secured notes payable	767,000	689,000													767,000	689,000
Total debt	1,397,553,000	1,397,308,000
Financial services credit facility	59,119,000	73,084,000															59,100,000	73,100,000
Other debt disclosures
Interest rate stated percentage			5.40%		8.40%		6.60%		5.40%		1.60%		0.25%
Letters of credit outstanding	88,600,000	93,600,000
Maximum borrowing capacity																	$ 100,000,000		$ 50,000,000	$ 50,000,000
Weighted average interest rate (as a percent)																	3.40%	3.40%