Equity (Details) - USD ($)						1 Months Ended	12 Months Ended
	Feb. 20, 2019	Dec. 10, 2018	Nov. 06, 2018	Jun. 11, 2018	May 04, 2018	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 15, 2023	Dec. 27, 2018	Dec. 05, 2018	Nov. 01, 2018	Dec. 31, 2015
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock							$ 880,000,000	$ 0	$ 0
Preferred Stock, Par or Stated Value Per Share						$ 0.01	$ 0.01				$ 0.01
Common stock, shares authorized						400,000,000	400,000,000	400,000,000
Preferred Stock, Shares Authorized						20,000,000	20,000,000
Common stock, par value						$ 0.01	$ 0.01	$ 0.01
Common Stock Aggregate Sale Price													$ 500,000,000
Shares, Issued						372,363,000	372,363,000	337,016,000	323,160,000					319,110,000
Dividends, Common Stock, Cash							$ 273,500,000	$ 229,400,000	$ 205,700,000
Dividends Payable, Date to be Paid							Feb. 20, 2019
Dividends Payable, Date of Record							Feb. 11, 2019
Common Stock, Shares, Outstanding						372,363,656	372,363,656	337,015,806
Preferred Stock, Shares Outstanding						420,000	420,000
Common Stock, Dividends, Per Share, Declared							$ 0.780	$ 0.700	$ 0.64
Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Dividend Rate, Percentage				5.65%
Preferred Stock, Par or Stated Value Per Share				$ 1,000
Preferred Stock, Shares Issued				400,000
Preferred Stock, Dividend Rate, Initial Margin				2.843%
Preferred Stock, Dividend Rate, Initial Margin Plus 1.000%				1.00%
Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Dividend Rate, Percentage						3.632%
Preferred Stock, Liquidation Preference Per Share						$ 25,000	25,000				$ 0.01
Depositary Stock Liquidation Preference						$ 25	$ 25
Preferred Stock, Shares Issued											20,000
Preferred Stock, Dividend Rate, Initial Margin						6.50%
Preferred Stock, Dividend Rate, Initial Margin Plus 1.000%						1.00%
Preferred Stock Depositary Shares Issued												20,000,000
Preferred Stock, Liquidation Preference, Value						$ 500,000,000	$ 500,000,000
Gross Proceeds | Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement				$ 400,000,000
Gross Proceeds | Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock						500,000,000
Net Proceeds | Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement				$ 393,900,000
Net Proceeds | Series B Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Preferred Stock and Preference Stock						$ 486,100,000
Common Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Sale of Stock, Price Per Share					$ 24.28
Common stock, par value					$ 0.01
Shares, Issued					24,964,163	376,326,000	376,326,000	340,813,000	326,664,000					322,181,000
Dividends, Common Stock, Cash							$ 0	$ 0	$ 0
Common Stock | Gross Proceeds
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement					$ 606,000,000
Common Stock | Net Proceeds
Forward Contract Indexed to Issuer's Equity [Line Items]
Proceeds from Issuance of Private Placement					$ 599,600,000
At The Market Program
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares		4,708,098
Common Stock Aggregate Sale Price						$ 500,000,000	500,000,000
ATM Program Equity Remaining Available for Issuance							$ 309,400,000
Derivative, Forward Price		$ 26.55					$ 26.51
Option Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value						$ 124,800,000	$ 124,800,000
Forward Agreement
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value			$ 167,700,000
Derivative, Forward Price			$ 26.43
Subsequent Event
Forward Contract Indexed to Issuer's Equity [Line Items]
Dividends, Common Stock, Cash	$ 0.20
Subsequent Event | Series A Preferred Stock
Forward Contract Indexed to Issuer's Equity [Line Items]
Preferred Stock, Liquidation Preference Per Share										$ 1,000