Organization and Basis of Presentation - Accumulated Other Comprehensive Income Summary (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2015 USD ($)
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning	$ (56,003)
Balance at the end	(52,649)
Other Comprehensive Income (Loss), Available-for-sale Securities Change In Unrealized Gain (Loss) During Period [Roll Forward]
Balance at beginning	4,551
Change in fair value of marketable securities	(2,121)
Balance at the end	2,497
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning	(51,452)
Other comprehensive income before reclassification	(4,515)
Amounts reclassified from accumulated other comprehensive loss	5,815
Other comprehensive income	1,300
Balance at the end	(50,152)
Essex Portfolio, L.P. [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Balance at beginning	(53,980)
Balance at the end	(50,515)
Other Comprehensive Income (Loss), Available-for-sale Securities Change In Unrealized Gain (Loss) During Period [Roll Forward]
Balance at beginning	4,624
Change in fair value of marketable securities	(2,121)
Balance at the end	2,503
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at beginning	(49,356)
Other comprehensive income before reclassification	(4,667)
Amounts reclassified from accumulated other comprehensive loss	6,011
Other comprehensive income	1,344
Balance at the end	(48,012)
Accumulated Other Comprehensive Income (Loss) [Member] | Essex Portfolio, L.P. [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Other comprehensive income before reclassification	(2,546)
Amounts reclassified from accumulated other comprehensive loss	6,011
Other comprehensive income	3,465
Other Comprehensive Income (Loss), Available-for-sale Securities Change In Unrealized Gain (Loss) During Period [Roll Forward]
Change in fair value of marketable securities	(2,121)
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income	(2,121)
Accumulated Other Comprehensive Income (Loss) [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Roll Forward]
Other comprehensive income before reclassification	(2,461)
Amounts reclassified from accumulated other comprehensive loss	5,815
Other comprehensive income	3,354
Other Comprehensive Income (Loss), Available-for-sale Securities Change In Unrealized Gain (Loss) During Period [Roll Forward]
Change in fair value of marketable securities	(2,054)
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive income	$ (2,054)