Equity Distribution Program (Details) - USD ($) |
12 Months Ended | ||
---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
Class of Stock [Line Items] | |||
Proceeds from issuance of common stock | $ 9,700,000 | $ 41,900,000 | $ 465,800,000 |
Equity Distribution Program | |||
Class of Stock [Line Items] | |||
Stock program, maximum amount authorized | $ 500,000,000 | ||
Proceeds from issuance of common stock | $ 0 |