Equity Incentive Plan - Equity Non-cash Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
2011 Equity Incentive Plan | Common Stock
Equity Incentive Plan
Number of days of average trailing stock price used to calculate number of shares of common stock granted			10 days
General and Administrative Expenses
Equity Incentive Plan
Share-based compensation	$ 2,388	$ 2,044	$ 4,775	$ 5,649
General and Administrative Expenses | Independent Director
Equity Incentive Plan
Share-based compensation	90	90	178	170
General and Administrative Expenses | Restricted stock
Equity Incentive Plan
Share-based compensation	590	534	1,182	1,092
General and Administrative Expenses | LTIP Units
Equity Incentive Plan
Share-based compensation	1,171	1,098	2,341	3,893
General and Administrative Expenses | LTIP Units | Geoffrey G. Jervis | 2011 Equity Incentive Plan
Equity Incentive Plan
Share-based compensation				1,600
General and Administrative Expenses | Performance shares
Equity Incentive Plan
Share-based compensation	$ 537	$ 322	$ 1,074	$ 494