Segment Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) segment	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting [Abstract]
Number of reportable operating segments defined by geographical regions | segment	3
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	$ 1,450,628	$ 1,390,870	$ 1,354,325
Total net operating income	1,052,933	1,005,536	978,939
Corporate-level property management expenses	(32,899)	(31,062)	(30,156)
Depreciation and amortization	(483,750)	(479,884)	(468,881)
General and administrative	(54,262)	(53,451)	(41,385)
Expensed acquisition and investment related costs	(168)	(194)	(1,569)
Impairment loss	(7,105)	0	0
Gain (loss) on sale of real estate and land	(3,164)	61,861	26,423
Interest expense	(217,339)	(220,492)	(222,894)
Total return swap income	8,446	8,707	10,098
Interest and other income	46,298	23,010	24,604
Equity income from co-investments	112,136	89,132	86,445
Deferred tax expense on unrealized gain on unconsolidated co-investment	(1,457)	0	0
Gain (loss) on early retirement of debt, net	3,717	0	(1,796)
Gain on remeasurement of co-investment	31,535	1,253	88,641
Net income	464,448	413,599	458,043
Assets:
Net reportable operating segments - real estate assets	10,348,660	10,156,553
Real estate under development	546,075	454,629
Co-investments	1,335,339	1,300,140
Cash and cash equivalents, including restricted cash	81,094	151,395
Marketable securities	144,193	209,545
Notes and other receivables (includes related party receivables of $90.2 million and $11.1 million as of December 31, 2019 and December 31, 2018, respectively)	134,365	71,895
Operating lease right-of-use assets	74,744	0
Prepaid expenses and other assets	40,935	39,439
Total assets	12,705,405	12,383,596
Rental and Other Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	1,450,628	1,390,870	1,354,325
Management and Other Fees from Affiliates
Revenues from External Customers and Long-Lived Assets [Line Items]
Management and other fees from affiliates	9,527	9,183	9,574
Operating Segments | Southern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net operating income	434,267	421,274	407,771
Assets:
Net reportable operating segments - real estate assets	4,233,110	4,368,882
Operating Segments | Southern California | Rental and Other Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	610,240	592,281	574,552
Operating Segments | Northern California
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net operating income	420,320	385,483	371,597
Assets:
Net reportable operating segments - real estate assets	4,622,268	4,289,232
Operating Segments | Northern California | Rental and Other Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	569,556	522,561	505,313
Operating Segments | Seattle Metro
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net operating income	173,875	165,244	162,111
Assets:
Net reportable operating segments - real estate assets	1,481,061	1,485,040
Operating Segments | Seattle Metro | Rental and Other Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	245,476	236,525	229,871
Other Real Estate Assets
Revenues from External Customers and Long-Lived Assets [Line Items]
Total net operating income	24,471	33,535	37,460
Assets:
Net reportable operating segments - real estate assets	12,221	13,399
Other Real Estate Assets | Rental and Other Property
Revenues from External Customers and Long-Lived Assets [Line Items]
Total property revenues	$ 25,356	$ 39,503	$ 44,589