Discontinued Operations - Summary of Revenue and Expense Information for Properties Sold which Qualify for Discontinued Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue:
Rents									$ 421,505	$ 486,731	$ 483,682
Tenant reimbursements									70,629	85,722	84,879
Other									4,316	6,617	3,221
Total revenue	$ 132,086	$ 129,694	$ 127,181	$ 136,502	$ 153,992	$ 152,585	$ 145,648	$ 150,406	525,463	602,631	596,982
Expenses:
Property operating expenses									152,926	181,170	177,330
Real estate taxes									46,252	50,623	51,844
Depreciation and amortization									189,676	219,029	208,569
Interest income									1,236	1,224	3,974
Income from discontinued operations before gain on sale of interests in real estate									0	0	18
Net gain on disposition of discontinued operations									0	0	900
Total discontinued operations									$ 0	$ 0	918
Discontinued Operations [Member]
Revenue:
Rents											0
Tenant reimbursements											26
Other											0
Total revenue											26
Expenses:
Property operating expenses											8
Real estate taxes											0
Depreciation and amortization											0
Total operating expenses											8
Interest income											0
Income from discontinued operations before gain on sale of interests in real estate											18
Net gain on disposition of discontinued operations											900
Total discontinued operations											$ 918