Accounts Receivable, Notes Receivable, Allowance for Doubtful Accounts and Bad Debt - Allowance for Doubtful Accounts Receivable (Details) (Notes Receivable, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Notes Receivable
Total
Beginning balance	$ 5.6
Charge-offs	(3.4)
Recoveries	0
Provision	3.7
Ending balance	5.9
Ending Balance Individually Evaluated for Impairment
Beginning balance	5.6
Charge-offs	(3.4)
Recoveries	0
Provision	3.7
Ending balance	5.9
Ending Balance Collectively Evaluated for Impairment
Beginning balance	0
Charge-offs	0
Recoveries	0
Provision	0
Ending balance	$ 0