Regulatory Capital and Dividends - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Feb. 09, 2016
Banking and Thrift [Abstract]
Dividends available	$ 192,712,000
Dividend reinvestment and stock purchase plan, stockholder's maximum amount of cash payments per quarter in purchase of common stock	$ 2,500
Stock repurchase program		$ 15,000,000