Stockholders' Equity (Details) (USD $)	0 Months Ended	3 Months Ended	0 Months Ended
	Jan. 28, 2015	Mar. 31, 2015	Jun. 03, 2014 Y	Feb. 17, 2015	Mar. 18, 2015	Dec. 31, 2014	Mar. 27, 2018
Class of Stock [Line Items]
Common stock, shares outstanding		153,402,107				153,113,945
Shares of its Common Stock in connection with the redemption of an equal number of OP Units (in shares)		258,599
Shares of Common Stock upon the exercise of options to purchase Common Stock by certain employees (in shares)		5,909
Dividend paid on common stock (in dollars per share)	$ 5.15
Dividends Payable, Amount Per Share					$ 0.65
Common Stock, Value, Issued		$ 1,534,000				$ 1,531,000
New ATM program [Member]
Class of Stock [Line Items]
At the market stock offering program, aggregate value of common stock			600,000,000
At Market Stock Offering Program Maximum Length Of Sale In Years			3
Common Stock, Value, Issued		$ 0
Quarter 4 2014 [Member]
Class of Stock [Line Items]
Dividend payable date		Jan. 28, 2015
Dividend shareholder of record date		Dec. 31, 2014
Quarter 1 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		Apr. 30, 2015
Dividend shareholder of record date		Mar. 31, 2015
Dividends payable, date declared		Mar. 18, 2015
Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Dividend paid on common stock (in dollars per share)				$ 32.8125
Dividends Payable, Amount Per Share					$ 32.8125
Series B, Shares Outstanding (in shares)		80,000				80,000
Series B, Dividend Rate, Percentage		5.25%
Series B, Liquidation Preference Per Share (dollars per share)		$ 2,500.00				$ 2,500
Ratio of depository shares to shares of Series B Preferred Stock		0.01
Series B Cumulative Redeemable Preferred Stock [Member] | Quarter 1 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		Feb. 17, 2015
Series B Cumulative Redeemable Preferred Stock [Member] | Quarter 2 2015 [Member]
Class of Stock [Line Items]
Dividend payable date		May 15, 2015
Dividend shareholder of record date		May 05, 2015
Dividends payable, date declared		Mar. 18, 2015
Depository shares of Series B Cumulative Redeemable Preferred [Member]
Class of Stock [Line Items]
Series B, Shares Outstanding (in shares)		8,000,000
Series B, Liquidation Preference Per Share (dollars per share)		$ 25.00					$ 25.00
Subsequent Event [Member] | Series B Cumulative Redeemable Preferred Stock [Member]
Class of Stock [Line Items]
Series B, Liquidation Preference Per Share (dollars per share)							$ 2,500.00