Noncontrolling Interests on the Company's Consolidated Financial Statements (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
Mar. 31, 2016	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Noncontrolling Interest [Line Items]
Common general partnership interest in the Operating Partnership (percentage)	97.20%	97.20%	98.10%	98.00%
Common limited partnership interest in the Operating Partnership (percentage)	2.80%	2.80%	1.90%	2.00%
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Aggregate value upon redemption of outstanding noncontrolling common units	$ 158.8	$ 158.8	$ 112.0
Brannan St Project [Member]
Noncontrolling Interest [Line Items]
Common units issued	867,701	867,701
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01

Number of shares of equity interests issued or issuable to acquire entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(4)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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Face amount or stated value per share of common stock.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 3A
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-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
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-Paragraph 3A
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-URI http://asc.fasb.org/extlink&oid=65877616&loc=SL6540498-122764

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