Fair Value Measurement - Carrying and Fair Value Amounts (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, Recourse and Nonrecourse	$ 278,115		$ 290,130
Fair Value, Inputs, Level 3 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit Agreement Loan	70,000		70,000
Fair Value, Inputs, Level 3 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Credit Agreement Loan	69,601	[1]	70,444	[1]
Fair Value, Inputs, Level 3 [Member] | Senior Notes [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes payable	200,000		208,333
Fair Value, Inputs, Level 3 [Member] | Senior Notes [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Senior notes payable	225,865	[1]	243,118	[1]
Held-to-Maturity [Member] | Fair Value, Inputs, Level 1 [Member] | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity marketable securities	117,202		111,430
Held-to-Maturity [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Held-to-maturity marketable securities	$ 116,915		$ 111,525

[1] The fair values of the senior notes payable and Credit Agreement (as defined under “Credit Agreement” in Note 12) loan are based on borrowing rates available to us for long-term loans with similar terms, average maturities, and credit risk.