Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 01, 2024	Apr. 04, 2019	May 09, 2016	Aug. 05, 2015	Aug. 06, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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
Number of shares authorized to be repurchased										2,765,000
Common stock repurchases						$ 134,778	$ 30,670	$ 164,724	$ 30,670
Shares authorized to be repurchased						117,230		117,230
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)						1,759,849	400,000	2,147,770	400,000
Common stock repurchases						$ 1,760	$ 400	$ 2,148	$ 400
2016 and 2018 Share Repurchase Program
Class of Stock [Line Items]
Common stock repurchases						$ 134,800		$ 164,700
Average cost of common stock shares repurchased (in usd per share)						$ 76.59		$ 76.70	$ 76.67
2016 and 2018 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)						1,759,849		2,147,770	400,000
Common stock repurchases									$ 30,700
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 total common shares outstanding								3.00%
Forecast | Series D Preferred Stock
Class of Stock [Line Items]
Variable dividend rate after August 1, 2024	3.859%
Subsequent Event
Class of Stock [Line Items]
Common stock repurchases (in shares)					307,230
Treasury stock acquired					$ 23,000