Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands					12 Months Ended
	Jun. 01, 2020	Sep. 19, 2018	Sep. 15, 2016	Jun. 15, 2015	Dec. 31, 2020	Dec. 31, 2018	Dec. 31, 2019	Jul. 25, 2017	Aug. 28, 2015
Stockholders' Equity Note [Abstract]
Subsidiary equity balance					$ 4,000,000
Class of Stock [Line Items]
Preferred Stock, Shares Issued					364,458		264,458
Purchase of stock, value						$ 537
Series C Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Shares Issued				2,600,000
Preferred Stock, Dividend Rate, Percentage				6.125%
Preferred Stock, Liquidation Preference Per Share				$ 1,000
Preferred Stock, Redemption Price Per Share				$ 1,000
Preferred Stock, Dividend Payment Terms				Shares of the Series C Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series C Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment.
Preferred Stock, Redemption Terms				The Series C Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on June 15, 2020, or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends.
Preferred Stock, Voting Rights				Except in certain limited circumstances, the Series C Preferred Stock does not have any voting rights.
Stock repurchase program authorized amount									$ 10,000
Remaining authorized repurchase amount					$ 10,000
Series D Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Shares Issued			4,000,000.0
Preferred Stock, Dividend Rate, Percentage			5.375%
Preferred Stock, Liquidation Preference Per Share			$ 1,000
Preferred Stock, Redemption Price Per Share			$ 1,000
Preferred Stock, Participation Rights			Dividends on the Series D Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 5.375%.
Preferred Stock, Dividend Payment Terms			Shares of the Series D Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series D Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment.
Preferred Stock, Redemption Terms			The Series D Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on September 15, 2021, or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends.
Preferred Stock, Voting Rights			Except in certain limited circumstances, the Series D Preferred Stock does not have any voting rights.
Stock repurchase program authorized amount								$ 15,000
Remaining authorized repurchase amount					14,000
Series E Preferred Stock
Class of Stock [Line Items]
Preferred Stock, Shares Issued		4,000,000.0
Preferred Stock, Dividend Rate, Percentage		5.875%
Preferred Stock, Liquidation Preference Per Share		$ 1,000
Preferred Stock, Redemption Price Per Share		$ 1,000
Preferred Stock, Participation Rights		Dividends on the Series E Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 5.875%.
Preferred Stock, Dividend Payment Terms		Shares of the Series E Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series E Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment.
Preferred Stock, Redemption Terms		The Series E Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on December 15, 2023, or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends.
Preferred Stock, Voting Rights		Except in certain limited circumstances, the Series E Preferred Stock does not have any voting rights.
Series F Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Issued	4,000,000.0
Preferred Stock, Dividend Rate, Percentage	5.625%
Preferred Stock, Liquidation Preference Per Share	$ 1,000
Preferred Stock, Redemption Price Per Share	$ 1,000
Preferred Stock, Participation Rights	Dividends on the Series F Preferred Stock are payable quarterly in arrears only when, as and if declared by the Board of Directors at a rate per annum equal to 5.625%.
Preferred Stock, Dividend Payment Terms	Shares of the Series F Preferred Stock have priority over the Corporation’s common stock with regard to the payment of dividends and distributions upon liquidation, dissolution or winding up. As such, the Corporation may not pay dividends on or repurchase, redeem, or otherwise acquire for consideration shares of its common stock unless dividends for the Series F Preferred Stock have been declared for that period, and sufficient funds have been set aside to make payment.
Preferred Stock, Redemption Terms	The Series F Preferred Stock may be redeemed by the Corporation at its option (i) either in whole or in part, from time to time, on any dividend payment date on or after the dividend payment date occurring on September 15, 2025, or (ii) in whole but not in part, at any time within 90 days following certain regulatory capital treatment events, in each case at a redemption price of $1,000 per share (equivalent to $25 per depositary share), plus any applicable dividends.
Preferred Stock, Voting Rights	Except in certain limited circumstances, the Series F Preferred Stock does not have any voting rights.
Treasury Stock
Class of Stock [Line Items]
Stock repurchase program authorized amount					$ 250,000
Treasury stock shares acquired (in shares)					8,200,000
Treasury stock carrying basis					$ 177,000
Treasury stock acquired average cost per share (in usd per share)					$ 21.62
Common Stock [Member]
Class of Stock [Line Items]
Payments Related to Tax Withholding for Share-based Compensation					$ 9,000
Shares Paid for Tax Withholding for Share Based Compensation					397,969
Minimum tax withholding settlement average cost per share (in usd per share)					$ 21.59
Remaining authorized repurchase amount					$ 113,000