Stock-Based Compensation (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014	Sep. 30, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Capitalized stock-based compensation	$ (615)	[1]	$ (620)	[1]	$ (2,026)	$ (1,567)
Stock-based compensation, net of capitalization	2,350		3,067		6,885	9,227
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	2,915		3,622		8,747	10,600
Shares granted					256,941
Weighted average grant date fair value (in dollars per share)					$ 48.14
Director [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$ 50	[2]	$ 65	[2]	$ 164	$ 194

[1] Includes compensation expense specifically identifiable to development and leasing activities.

[2] Includes amortization of the grant date fair value of restricted stock awards over the respective vesting periods.