Fair Value of Assets and Liabilities - Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Fair Value of Financial Instruments
Senior notes	$ 2,360,063	$ 2,357,497
Mortgage notes payable, net	$ 326,202	335,241
Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Interest rate (as a percent)	3.75%
Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Interest rate (as a percent)	3.60%
Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	4.00%
Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Interest rate (as a percent)	4.15%
Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Interest rate (as a percent)	4.25%
Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Interest rate (as a percent)	4.50%
Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Interest rate (as a percent)	5.875%
Carrying Amount
Fair Value of Financial Instruments
Mortgage notes payable, net	$ 326,202	335,241
Fair value of financial instruments	2,686,265	2,692,738
Carrying Amount \| Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Senior notes	349,524	349,239
Carrying Amount \| Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Senior notes	399,343	399,146
Carrying Amount \| Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	296,966	296,735
Carrying Amount \| Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	297,001	296,736
Carrying Amount \| Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Senior notes	338,307	337,736
Carrying Amount \| Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Senior notes	378,260	377,329
Carrying Amount \| Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Senior notes	300,662	300,576
Fair Value
Fair Value of Financial Instruments
Mortgage notes payable, net	328,809	336,365
Fair value of financial instruments	2,721,349	2,665,550
Fair Value \| Senior unsecured notes, 3.75% interest rate, due in 2019
Fair Value of Financial Instruments
Senior notes	350,586	348,903
Fair Value \| Senior unsecured notes, 3.60% interest rate, due in 2020
Fair Value of Financial Instruments
Senior notes	401,040	399,146
Fair Value \| Senior unsecured notes, 4.00% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	300,845	295,047
Fair Value \| Senior unsecured notes, 4.15% interest rate, due in 2022
Fair Value of Financial Instruments
Senior notes	303,428	296,736
Fair Value \| Senior unsecured notes, 4.25% interest rate, due in 2024
Fair Value of Financial Instruments
Senior notes	336,137	337,736
Fair Value \| Senior unsecured notes, 4.50% interest rate, due in 2025
Fair Value of Financial Instruments
Senior notes	387,404	377,329
Fair Value \| Senior unsecured notes, 5.875% interest rate, due in 2046
Fair Value of Financial Instruments
Senior notes	$ 313,100	$ 274,288

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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section S99
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-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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