Acquisitions (Narrative) (Details) - USD ($) $ in Thousands			1 Months Ended	9 Months Ended
	Sep. 25, 2017	Oct. 01, 2016	Nov. 30, 2017	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Brokered deposits					$ 1,961,125	$ 1,378,983
Common stock, shares issued (in shares)					142,677,449	142,025,720
Common stock					$ 142,678	$ 142,026
Other intangible assets					11,254	$ 13,223
Existing Borrower Relationships
Business Acquisition [Line Items]
Useful life				11 years
Trade Names
Business Acquisition [Line Items]
Useful life				10 years
Distribution Network
Business Acquisition [Line Items]
Useful life				8 years
Global One
Business Acquisition [Line Items]
Consideration transferred		$ 30,000
Common stock, shares issued (in shares)		821,000
Common stock		$ 26,592
Cash paid		$ 3,408
Adjustment in goodwill				$ 2,400
Adjustment in contingent consideration				$ 1,800
Earnout payment of stock and cash			$ 6,400
Earnout liability					11,300
Global One | Existing Borrower Relationships
Business Acquisition [Line Items]
Other intangible assets					9,600
Global One | Trade Names
Business Acquisition [Line Items]
Other intangible assets					962
Global One | Distribution Network
Business Acquisition [Line Items]
Other intangible assets					$ 506
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
World's Foremost Bank (WFB)
Business Acquisition [Line Items]
Brokered deposits	$ 1,100,000
Deposits portfolio, weighted average maturity, period	2 years 6 months 11 days
Weighted average rate of deposit, brokered	1.83%
Proceeds from fees	$ 75,000