Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Sep. 30, 2019	Mar. 31, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Liquidation preference value	$ 237,500
Carrying Amount	$ 228,485			$ 228,485
Common stock repurchases			$ 29,946
Average cost of common stock shares repurchased (in usd per share)			$ 77.19
Shares authorized to be repurchased (in shares)	1,165,000
Series B Preferred Stock
Class of Stock [Line Items]
Annual Dividend Rate	6.625%
Liquidation preference value	$ 80,000
Carrying Amount	$ 76,812			76,812
Series C Preferred Stock
Class of Stock [Line Items]
Annual Dividend Rate	6.60%
Liquidation preference value	$ 57,500
Carrying Amount	$ 55,285			55,285
Series D Preferred Stock
Class of Stock [Line Items]
Annual Dividend Rate	6.10%
Liquidation preference value	$ 100,000
Carrying Amount	$ 96,388			$ 96,388
Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)			387,921
Common stock repurchases			$ 388
2019 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Number of shares authorized to be repurchased		1,600,000
Percentage of outstanding common shares		3.00%