SCHEDULE III-Consolidated Real Estate and Accumulated Depreciation Rollforward (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Real estate assets
Balance, beginning of period		$ 1,995,417	$ 1,938,676	$ 1,687,276
Property acquisitions		0	0	270,082
Improvements	[1]	154,594	60,677	41,303
Cost of Real Estate Sold		0	0	(57,188)
Other	[1],[2]	(13,187)	(3,936)	(2,797)
Balance, end of period		2,136,824	1,995,417	1,938,676
Accumulated depreciation
Balance, beginning of period		318,581	270,494	234,595
Additions-depreciation	[1]	55,159	51,949	47,792
Cost of Real Estate Sold		0	0	(9,216)
Other	[1],[2]	(12,316)	(3,862)	(2,677)
Balance, end of period		$ 361,424	$ 318,581	$ 270,494

[1] Includes discontinued operations for 160 King Street, which was sold on December 4, 2012.

[2] Other deductions for the years ended December 31, 2014, 2013 and 2012 represent the write-off of fully depreciated assets.