Material Transactions Affecting Stockholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended	9 Months Ended
	Mar. 09, 2020	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Feb. 26, 2020	Feb. 25, 2020
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)			231,000		231,000
Preferred stock issued		$ (265)		$ 221,047
Net proceeds from the issuance of preferred stock		$ 221,200	$ 0	$ 221,047
Stock repurchase program, authorized amount						$ 200,000	$ 180,000
Common stock repurchased (in shares)			715,000
Total cost of common stock repurchased			$ 14,900
Depository Series A Shares
Class of Stock [Line Items]
Preferred stock, conversion rate (as a percent)		2.50%
Preferred stock, shares issued (in shares)		4,300,000		4,300,000
Preferred stock, fixed rate (as a percent)		7.00%
Depository Series C Shares
Class of Stock [Line Items]
Preferred stock, conversion rate (as a percent)		2.50%
Preferred stock, shares issued (in shares)		4,900,000		4,900,000
Preferred stock, fixed rate (as a percent)		7.00%
Depository Shares
Class of Stock [Line Items]
Preferred stock issued		$ 230,500
Bankmanagers Corporation
Class of Stock [Line Items]
Acquisitions, net of issuance costs (in shares)	4,930,231
Shares issued (in dollars per share)	$ 14.58