Unsecured senior notes payable (Details) - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended | ||
---|---|---|---|---|
Jun. 30, 2018 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Debt Instrument [Line Items] | ||||
Unsecured senior notes payable | $ 4,300,000 | |||
Ownership interest in subsidiary (as a percent) | 100.00% | |||
Outstanding Balance | $ 5,498,442 | |||
Proceeds from issuance of unsecured senior notes payable | 899,321 | $ 1,023,262 | $ 348,604 | |
4.00% and 4.70% Unsecured Senior Notes Payable | ||||
Debt Instrument [Line Items] | ||||
Outstanding Balance | $ 900,000 | |||
Proceeds from issuance of unsecured senior notes payable | 891,400 | |||
4.00% unsecured senior note payable | ||||
Debt Instrument [Line Items] | ||||
Outstanding Balance | $ 450,000 | $ 450,000 | ||
Maturity date | Jan. 15, 2024 | Jan. 15, 2024 | ||
Stated interest rate (as a percent) | 4.00% | 4.00% | ||
4.70% unsecured senior note payable | ||||
Debt Instrument [Line Items] | ||||
Outstanding Balance | $ 450,000 | $ 450,000 | ||
Maturity date | Jul. 01, 2030 | Jul. 01, 2030 | ||
Stated interest rate (as a percent) | 4.70% | 4.70% |