Stockholders' Equity - Preferred Stock (Details) - $ / shares	1 Months Ended		12 Months Ended
	May 31, 2016	Mar. 31, 2016	Dec. 31, 2019	Dec. 31, 2018
Series E Cumulative Redeemable Preferred Stock
Stockholders' equity
Number of shares of preferred stock sold (in shares)		4,600,000
Preferred stock, Cumulative Redeemable Preferred Stock, dividend rate (as a percent)			6.95%	6.95%
Liquidation preference (in dollars per share)		$ 25.00	$ 25.00	$ 25.00
Redemption price (in dollars per share)		$ 25.00
Series F Cumulative Redeemable Preferred Stock
Stockholders' equity
Number of shares of preferred stock sold (in shares)	3,000,000
Preferred stock, Cumulative Redeemable Preferred Stock, dividend rate (as a percent)			6.45%	6.45%
Liquidation preference (in dollars per share)	$ 25.00		$ 25.00	$ 25.00
Redemption price (in dollars per share)	$ 25.00