Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands					3 Months Ended		9 Months Ended
	Aug. 01, 2024	Apr. 04, 2019	May 09, 2016	Aug. 05, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, shares issued					23,750		23,750		13,750
Preferred stock, par value (in usd per share)					$ 1		$ 1		$ 1
Liquidation preference (per share)					$ 10,000		$ 10,000		$ 10,000
Liquidation preference value			$ 237,500
Carrying Amount					$ 228,485		$ 228,485		$ 132,097
Common stock repurchases					$ 40,016	$ 30,376	$ 204,740	$ 61,046
Shares authorized to be repurchased					1,165,000		1,165,000
Series B Preferred Stock
Class of Stock [Line Items]
Ownership per share				6.625%
Liquidation preference value				$ 80,000
Carrying Amount					$ 76,812		$ 76,812		76,812
Series C Preferred Stock
Class of Stock [Line Items]
Ownership per share			6.60%
Liquidation preference value			$ 57,500
Carrying Amount					55,285		55,285		55,285
Series D Preferred Stock
Class of Stock [Line Items]
Ownership per share		6.10%
Preferred stock, par value (in usd per share)		$ 1.00
Liquidation preference (per share)		$ 10,000
Liquidation preference value		$ 100,000
Carrying Amount					$ 96,388		$ 96,388		$ 0
Series D Depositary Shares
Class of Stock [Line Items]
Preferred stock, shares issued		4,000,000
Liquidation preference (per share)		$ 25
Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)					552,230	363,210	2,700,000	763,210
Common stock repurchases					$ 552	$ 363	$ 2,700	$ 763
2018 Share Repurchase Plan | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased									2,765,000
Common stock repurchases (in shares)					117,230
2019 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased					1,600,000		1,600,000
Percentage of outstanding common shares					3.00%
2016 and 2018 Share Repurchase Program
Class of Stock [Line Items]
Common stock repurchases					$ 40,000	$ 30,400	$ 204,700
Average cost of common stock shares repurchased (in usd per share)					$ 72.46	$ 83.63	$ 75.83	$ 79.99
2016 and 2018 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)					552,230	363,210	2,700,000	763,210
Common stock repurchases								$ 61,000
Forecast | Series D Preferred Stock
Class of Stock [Line Items]
Variable dividend rate after August 1, 2024	3.859%