Incentive Plans (Details Textual) (USD $) Share data in Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	5.3
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	2.5	0.3
Amortization of restricted stock awards and operating partnership units	$ 5,744,000	$ 3,300,000	$ 2,252,000
Severance Costs	6,159,000	0	0
Severance Costs Discontinued Operations	2,959,000	0	0
Restricted Stock [Member]
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	2,900,000
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	1 year 3 months 18 days
Allocated Share-based Compensation Expense	4,400,000	1,900,000	1,000,000
Amortization of restricted stock awards and operating partnership units	1,300,000	900,000	600,000
Stock Granted, Value, Share-based Compensation, Net of Forfeitures, Total	200,000	500,000	100,000
Severance Costs	2,200,000
Severance Costs Discontinued Operations	500,000
Restricted Stock Units (RSUs) [Member]
Allocated Share-based Compensation Expense		200,000
Amortization of restricted stock awards and operating partnership units		$ 300,000