Commitments and Contingencies (Details) (USD $)	1 Months Ended	12 Months Ended
	May 31, 2010	Dec. 31, 2013 property	Dec. 31, 2013 Ground	Dec. 31, 2012 Ground	Dec. 31, 2011 Ground	Dec. 31, 2013 Office	Dec. 31, 2012 Office	Dec. 31, 2011 Office
Commitments and Contingencies.
Insurance proceeds funded by insurers	$ 50,000,000
Minimum insurance coverage	50,000,000
Additional insurance proceeds	150,000,000
Lease Commitments
Properties subject to ground leases		28
Lease Commitments
Lease expense			40,042,000	43,421,000	42,284,000	4,057,000	2,004,000	2,047,000
Future minimum lease payments due under ground leases
2014		25,974,000
2015		30,991,000
2016		36,851,000
2017		36,863,000
2018		36,818,000
Thereafter		1,012,997,000
Total		1,180,494,000
Insurance
Insurance coverage, acts of terrorism		$ 1,000,000,000