Equity Based Compensation Plans (Details)		1 Months Ended	12 Months Ended				24 Months Ended
	Dec. 09, 2014 shares	Dec. 31, 2013 shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 09, 2015	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2011 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available (in shares) | shares			1,000,000
Exercise price as a percentage of fair market value of common stock on grant date, minimum (in hundredths)			100.00%
Life of options, minimum (in years)			5 years
Life of options, maximum (in years)			10 years
Accelerated share-based compensation cost			$ 3,500,000	$ 2,700,000
Intrinsic value of the options outstanding and fully vested			$ 20,800,000	$ 29,800,000
Average fair value of stock options granted (in dollars per share) | $ / shares			$ 21.65	$ 22.78		$ 20.56
Cap on the appreciation of the market price over the exercise price, option 1			$ 75	$ 75		$ 75
Cap on the appreciation of the market price over the exercise price, option 2			100	100		100
Cap on the appreciation of the market price over the exercise price, option 3			125	125		125
BRE Properties, Inc. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense			100,000	200,000
Merger and integration expenses			0	100,000		1,700,000
Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense			8,200,000	6,100,000		6,100,000
Stock-based compensation capitalized			500,000	300,000		400,000
Intrinsic value of options exercised			11,900,000	$ 19,400,000		$ 12,700,000
Unrecognized compensation cost			$ 5,000,000
Unrecognized compensation cost, period for recognition (in years)			2 years 9 months 15 days
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost			$ 5,900,000
Unrecognized compensation cost, period for recognition (in years)			2 years 2 months 12 days
Granted (in shares) | shares			49,183	56,177		22,014
2015 LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period	5 years
Share based compensation expense						$ 2,400,000
Unrecognized compensation cost, period for recognition (in years)			8 years 6 months
Granted (in shares) | shares	44,750
Units issued subject only to performance measurement | shares	24,000
Vesting percentage of units per year	20.00%
Percent of awards earned					95.75%
Conversion ratio, incentive units			1
Liquidity measurement period (in years)			10 years
Measurement period (in years)			10 years
Series Z Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period		4 years
Granted (in shares) | shares		50,500					154,500
Conversion ratio, incentive units							1
Incentive units conversion ratio							one-for-one
Long Term Incentive Plan 2014 Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, period for recognition (in years)			2 years 2 months 12 days
Vesting percentage of units per year		25.00%
Conversion ratio, incentive units			1
Liquidity measurement period (in years)			10 years
Measurement period (in years)			10 years
Vesting percentage for 2011 Z 1 Units to be convertible							100.00%
Long Term Incentive Plans - Z Units and 2014 LTIP Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share based compensation expense			$ 2,700,000	$ 3,500,000		6,000,000
Stock-based compensation capitalized			600,000	$ 500,000		$ 400,000
Unrecognized compensation cost			$ 3,600,000
Granted (in shares) | shares			0	0		44,750
Intrinsic value of vested and unvested LTIP units			$ 56,000,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period			0 years
Minimum [Member] | Series Z Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period			8 years
Vesting percentage of units per year							0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period			5 years
Maximum [Member] | Series Z Incentive Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Option grants to officers and employees vesting period			15 years
Vesting percentage of units per year							14.00%