Capital Stock - Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Class of Stock [Line Items]
Dividends on preferred stock	$ 18,438	$ 18,438	$ 55,313	$ 55,313
Series A Preferred Stock
Class of Stock [Line Items]
Dividends on preferred stock	$ 3,000	$ 3,000	$ 9,000	$ 9,000
Preferred stock dividends declared (in USD per share)	$ 0.50	$ 0.50	$ 1.50	$ 1.50
Series B Preferred Stock
Class of Stock [Line Items]
Dividends on preferred stock	$ 7,000	$ 7,000	$ 20,000	$ 20,000
Preferred stock dividends declared (in USD per share)	$ 0.50	$ 0.50	$ 1.50	$ 1.50
Series C Preferred Stock
Class of Stock [Line Items]
Dividends on preferred stock	$ 5,000	$ 5,000	$ 15,000	$ 15,000
Preferred stock dividends declared (in USD per share)	$ 0.484375	$ 0.484375	$ 1.453125	$ 1.453125
Series D Preferred Stock
Class of Stock [Line Items]
Dividends on preferred stock	$ 4,000	$ 4,000	$ 12,000	$ 12,000
Preferred stock dividends declared (in USD per share)	$ 0.50	$ 0.50	$ 1.50	$ 1.50