Stockholders' Equity (Narrative) (Details)									1 Months Ended	3 Months Ended			6 Months Ended		202 Months Ended
	Aug. 06, 2020 $ / shares	Jul. 01, 2020 $ / shares	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 15, 2020 USD ($) $ / shares shares	Mar. 02, 2020 USD ($)	Feb. 28, 2020 $ / shares shares	Feb. 14, 2020 $ / shares	Apr. 15, 2013 $ / shares shares	Mar. 31, 2020 quarter director	Jun. 30, 2020 USD ($) $ / shares shares	Jun. 30, 2019 $ / shares	Mar. 31, 2019 $ / shares	Jun. 30, 2020 USD ($) quarter director $ / shares shares	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) $ / shares shares	Dec. 31, 2019 $ / shares shares	Oct. 15, 2019 shares	Aug. 16, 2019 USD ($)	Dec. 31, 2013 shares	Aug. 31, 2005 shares
Stockholders' Equity
Common stock, cash dividends declared (in dollars per share)											$ 0.20	$ 0.20
Proceeds from issuance of redeemable preferred stock | $													$ 275,000,000	$ 0
Aggregate number of shares of common stock authorized (in shares) | shares			874,300,000							874,300,000			874,300,000		874,300,000	886,950,000
Number of shares authorized to be repurchased under the Repurchase Program (in shares) | shares																			10,000,000.0	4,000,000.0
Number of remaining shares authorized to be repurchased under the Repurchase Program (in shares) | shares			6,616,355							6,616,355			6,616,355		6,616,355
Number of shares called by warrant (in shares) | shares				37,039,106
Proceeds from issuance of warrants | $				$ 495,000,000.0									$ 14,041,000	$ 0
DRSPP
Stockholders' Equity
Aggregate number of shares of common stock authorized (in shares) | shares																	9,000,000.0
Shares of common stock authorized and available for issuance (in shares) | shares			8,800,000							8,800,000			8,800,000		8,800,000
Common shares issued through DRSPP (in shares) | shares										26,417			133,366		34,512,134
Net proceeds from shares issued through DRSPP | $										$ 48,429			$ 740,408		$ 287,300,000
Series B Preferred Stock
Stockholders' Equity
Preferred Stock, dividend rate													7.50%	7.50%
Preferred stock, shares issued | shares			8,000,000							8,000,000			8,000,000		8,000,000	8,000,000
Preferred stock, par value (in dollars per share)			$ 0.01							$ 0.01			$ 0.01		$ 0.01	$ 0.01
Dividend declared per share, preferred stock (in dollars per share)		$ 0.9375					$ 0.46875				$ 0.46875	$ 0.46875
Amount of preferred dividends in arrears | $										$ 7,500,000
Amount of preferred dividends in arrears (USD per share)			$ 0.93750
Series C Preferred Stock
Stockholders' Equity
Preferred Stock, dividend rate													6.50%
Preferred stock, shares issued | shares			11,000,000							11,000,000			11,000,000		11,000,000
Preferred stock, par value (in dollars per share)			$ 0.01							$ 0.01			$ 0.01		$ 0.01
Amount of preferred dividends in arrears | $													$ 5,900,000
Amount of preferred dividends in arrears (USD per share)													$ 0.53264
Preferred Stock | Series B Preferred Stock
Stockholders' Equity
Preferred Stock, dividend rate								7.50%					7.50%	7.50%
Preferred stock, shares issued | shares								8,000,000.0
Preferred stock, par value (in dollars per share)								$ 0.01
Preferred stock, liquidation preference (in dollars per share)			$ 25.00					25.00		$ 25.00			$ 25.00		$ 25.00	$ 25
Preferred stock, redemption price (in dollars per share)								$ 25.00
Maximum quarters without dividends to get voting rights, in quarters | quarter													6
Number of additional directors that can be elected by preferred stock holders | director													2
Percentage required for making material changes								66.67%
Preferred Stock | Series C Preferred Stock
Stockholders' Equity
Preferred Stock, dividend rate						6.50%
Preferred stock, shares issued | shares						11,000,000.0
Preferred stock, par value (in dollars per share)						$ 0.01
Preferred stock, liquidation preference (in dollars per share)						25.00
Preferred stock, redemption price (in dollars per share)						$ 25.00
Maximum quarters without dividends to get voting rights, in quarters | quarter									6
Number of additional directors that can be elected by preferred stock holders | director									2
Shares reclassified to redeemable capital stock (in shares) | shares						12,650,000
Proceeds from issuance of redeemable preferred stock | $					$ 266,000,000.0
Warrant
Stockholders' Equity
Proceeds from issuance of warrants | $				$ 14,000,000.0
At The Market
Stockholders' Equity
At-the-market, maximum potential proceeds | $																		$ 400,000,000.0
Sales commission of gross sales price																		2.00%
Number of shares issued (in shares) | shares										0
Value remaining outstanding for future offerings | $			$ 390,000,000.0							$ 390,000,000.0			$ 390,000,000.0		$ 390,000,000.0
LIBOR | Preferred Stock | Series C Preferred Stock
Stockholders' Equity
Debt instrument, basis spread on variable rate						5.345%
Exercise Price Range One
Stockholders' Equity
Warrant exercise price (usd per share)				$ 1.66
Exercise Price Range Two
Stockholders' Equity
Warrant exercise price (usd per share)				$ 2.08
Debt
Stockholders' Equity
Proceeds from issuance of warrants | $				$ 481,000,000.0
Subsequent Event
Stockholders' Equity
Common stock, cash dividends declared (in dollars per share)	$ 0.05
Subsequent Event | Series B Preferred Stock
Stockholders' Equity
Dividend declared per share, preferred stock (in dollars per share)		0.93750
Subsequent Event | Series C Preferred Stock
Stockholders' Equity
Dividend declared per share, preferred stock (in dollars per share)		$ 0.53264