Accounts Receivable, Notes Receivable, Allowance for Doubtful Accounts and Bad Debt - Modification of Terms (Details) (Notes Receivable, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 contract customer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	11
Number of notes	34
Pre-modification investment	$ 17.1
Post-modification investment	17.1
International
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	11
Number of notes	34
Pre-modification investment	17.1
Post-modification investment	17.1
International | Customer One
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	4.0
Number of notes consolidated into one	12
Contract extension tern	28 months
International | Customer Two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	2.3
Contract extension tern	9 months
International | Customer three
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
International | Customer Three, Note One
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-modification investment	1.4
Number of notes consolidated into one	4
Contract extension tern	5 months
International | Customer Three, Note Two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Post-modification investment	0.2
Contract extension tern	7 months
International | Customer Four
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	3.1
Number of notes consolidated into one	3
Contract extension tern	4 months
International | Customer Five
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	0.5
Contract extension tern	21 months
International | Customer Six
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	0.3
Contract extension tern	27 months
International | Customer Seven
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	0.1
Contract extension tern	21 months
International | Customer Eight
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	0.7
Number of notes consolidated into one	2
Contract extension tern	15 months
International | Customer Nine
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	0.2
Number of notes consolidated into one	2
Contract extension tern	14 months
International | Customer Ten
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	2.5
Number of notes consolidated into one	5
Contract extension tern	24 months
International | Customer Eleven
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of customers	1
Post-modification investment	$ 1.8
Contract extension tern	34 months