Contractual interest rate for funds borrowed, under the debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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The cash inflow from the issuance of long-term debt that is not secured by collateral. Excludes proceeds from tax exempt unsecured debt.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585

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Equivalent Number Of Common Stock On Conversion Of Preferred Shares.

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Subsequent Events (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended
Subsequent Events (Details) - USD ($) $ in Thousands	Feb. 28, 2019	Feb. 15, 2019	Mar. 31, 2011	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Subsequent Event [Line Items]
Proceeds from issuance of senior unsecured notes				$ 2,824,176	$ 7,500	$ 693,560
Series I Preferred Stock
Subsequent Event [Line Items]
Common stock conversion rate			0.8460
Senior Unsecured Notes
Subsequent Event [Line Items]
Proceeds from issuance of senior unsecured notes				2,850,000	7,500	705,000
Redemption of debt				$ 1,450,000	$ 5,000	$ 850,000
Subsequent Event \| Series I Preferred Stock
Subsequent Event [Line Items]
Common stock conversion rate	0.8857
Subsequent Event \| Senior Unsecured Notes \| Senior Unsecured Notes Due 2024
Subsequent Event [Line Items]
Proceeds from issuance of senior unsecured notes		$ 500,000
Interest rate		3.625%
Subsequent Event \| Senior Unsecured Notes \| Senior Unsecured Notes Due 2029
Subsequent Event [Line Items]
Proceeds from issuance of senior unsecured notes		$ 550,000
Interest rate		4.125%
Subsequent Event \| Senior Unsecured Notes \| Senior Unsecured Notes Due 2019
Subsequent Event [Line Items]
Interest rate		4.125%
Redemption of debt		$ 600,000
Subsequent Event \| Senior Unsecured Notes \| Senior Unsecured Notes Due 2020
Subsequent Event [Line Items]
Interest rate		6.125%
Redemption of debt		$ 450,000