Acquisitions (Details) - USD ($) $ in Thousands			12 Months Ended
	Sep. 25, 2017	Oct. 01, 2016	Dec. 31, 2018	Nov. 30, 2018	Dec. 31, 2017	Nov. 30, 2017
Business Acquisition [Line Items]
Brokered deposits			$ 1,548,030		$ 1,961,125
Common stock, shares issued (in shares)			143,300,449		142,677,449
Fair value of common stock issued			$ 143,300		$ 142,678
Minimum
Business Acquisition [Line Items]
Period of additional annual payments		3 years
Maximum
Business Acquisition [Line Items]
Period of additional annual payments		5 years
World's Foremost Bank (WFB)
Business Acquisition [Line Items]
Deposits portfolio, weighted average maturity, period	2 years 6 months 11 days
Weighted average rate of deposit, brokered	1.83%
World's Foremost Bank (WFB)
Business Acquisition [Line Items]
Brokered deposits	$ 1,100,000
Proceeds from fees	$ 75,000
Global One
Business Acquisition [Line Items]
Consideration transferred		$ 30,000
Common stock, shares issued (in shares)		821,000		199,000		118,000
Fair value of common stock issued		$ 26,600		$ 7,400		$ 5,500
Cash paid		$ 3,400
Earnout payments, cash				$ 1,200		$ 892
Increase (decrease) in earnout liabilities			11,700
Earnout liability			$ 14,400
Global One | Minimum
Business Acquisition [Line Items]
Potential additional payments based on earnings, period		3 years
Global One | Maximum
Business Acquisition [Line Items]
Potential additional payments based on earnings, period		5 years