Shareholders' Equity, Capital Ratios and Other Regulatory Matters - Shareholders' Equity (Details) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended
	May 05, 2019	May 09, 2016	Aug. 05, 2015	Mar. 31, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Liquidation preference value		$ 137,500
Carrying Amount				$ 132,097	$ 132,097
Number of shares authorized to be repurchased				2,765,000
Common stock repurchases				$ 29,946
Shares authorized to be repurchased				1,877,079
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
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
Subsequent Event
Class of Stock [Line Items]
Common stock repurchases (in shares)	353,200
Treasury stock acquired	$ 28,200
Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)				387,921
Common stock repurchases				$ 388
2016 and 2018 Share Repurchase Program
Class of Stock [Line Items]
Common stock repurchases				$ 29,900
Average cost of common stock shares repurchased (in usd per share)				$ 77.19
2016 and 2018 Share Repurchase Program | Common Stock
Class of Stock [Line Items]
Common stock repurchases (in shares)				387,921