Significant Accounting Policies and Practices (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 entity	Dec. 31, 2012
Principles of Consolidation
Number of variable interest entities	38
Allowance for Doubtful Accounts
Allowance for doubtful accounts	$ 695	$ 506
Joint ventures | Consolidated variable interest entities
Principles of Consolidation
Number of variable interest entities	29
Joint ventures | Voting Interest Model Entities
Principles of Consolidation
Number of variable interest entities	9
Joint ventures | Voting Interest Model Entities | Minimum
Principles of Consolidation
Ownership percentage	20.00%
Joint ventures | Voting Interest Model Entities | Maximum
Principles of Consolidation
Ownership percentage	50.00%