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, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	$ 24,970
Right to purchase land		3,536
Deferred Compensation Plan Assets, Fair Value Disclosure	775	805
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	24,970
Right to purchase land		0
Deferred Compensation Plan Assets, Fair Value Disclosure	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Right to purchase land		0
Deferred Compensation Plan Assets, Fair Value Disclosure	775	805
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments, Fair Value Disclosure	0
Right to purchase land		3,536
Deferred Compensation Plan Assets, Fair Value Disclosure	$ 0	$ 0