Debt and Credit Facilities (Details2)	3 Months Ended	6 Months Ended		12 Months Ended
	Mar. 31, 2015 USD ($)	Jun. 30, 2015 USD ($) item	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2011 USD ($)
Debt
Decrease in debt		$ 126,481,000	$ 0
Letters of credit outstanding		17,500,000		$ 33,300,000
Financial services credit facilities		$ 122,607,000		129,389,000
5.4 percent senior notes due January 2015
Debt
Decrease in debt	$ 126,500,000
Interest rate stated percentage	5.40%	5.40%
Nonrecourse secured notes
Debt
Secured notes payable		$ 24,800,000		$ 5,800,000
Credit facility
Debt
Term of credit facility				4 years
Maximum borrowing capacity		$ 300,000,000		$ 300,000,000
Maximum borrowing capacity after future increase				450,000,000.0
Number of extensions | item		2
Extension term		1 year
Ownership interest in subsidiaries, who guarantee the funds borrowed		100.00%
Unused borrowing capacity		$ 213,500,000		232,300,000
Letter of credit subfacility
Debt
Maximum borrowing capacity				150,000,000.0
Outstanding amount of unsecured letters of credit		$ 86,500,000		67,700,000
Swing line facility
Debt
Maximum borrowing capacity				$ 25,000,000.0
Comerica Bank | Repurchase credit facility.
Debt
Weighted-average effective interest rate (percentage)		2.90%		3.20%
JPMorgan Chase Bank, N.A. (JPM) | Repurchase credit facility.
Debt
Maximum borrowing capacity				$ 100,000,000.0	$ 50,000,000.0
Financial services credit facilities		$ 59,300,000		80,900,000
RMCMC | Comerica Bank | Warehouse line of credit
Debt
Maximum borrowing capacity				50,000,000
Financial services credit facilities		$ 63,300,000		$ 48,500,000
Weighted-average effective interest rate (percentage)		3.00%		3.00%
Minimum | RMCMC | Comerica Bank | Warehouse line of credit
Debt
Maximum borrowing capacity				$ 50,000,000
Maximum | RMCMC | Comerica Bank | Warehouse line of credit
Debt
Maximum borrowing capacity				$ 100,000,000