Fair Value Measurements - Fair Value Assets Measured on a Non-recurring Basis (Details) (Fair Value, Measurements, Nonrecurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Development projects in progress	$ 0	$ 0
Land held for sale	0
Right to purchase land		0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Development projects in progress	0	0
Land held for sale	0
Right to purchase land		0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Development projects in progress	0	6,377
Land held for sale	0
Right to purchase land		1,600
Total
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Development projects in progress	0	6,377
Land held for sale	0
Right to purchase land		$ 1,600