Commitments and Contingencies (Narrative) (Details) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) properties $ / shares shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Sep. 30, 2017 branches	Dec. 31, 2014 USD ($)
Commitments and Contingencies Disclosure [Abstract]
Number of non-cancelable operating leases | properties	233
Rent expense	$ 38,400	$ 38,500	$ 38,300
Rent income	2,200	2,000	$ 1,400
Standby letters of credit, required to perform on financial guarantees	0	150
Standby letters of credit that expire within one year	47,700
Standby letters of credit that expire thereafter	23,300
Standby letters of credit fees	863	818
Residential mortgage loan repurchase reserve liability	1,200
Loss Contingencies [Line Items]
Litigation settlement other company owned stock					$ 4,400,000
Number Of Stores To Be Consolidated | branches				30
Financing Receivable, Recorded Investment, Past Due [Line Items]
GNMA loans, right to repurchase	87,292	69,651
Financing Receivables, Equal to Greater than 90 Days Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
GNMA loans, right to repurchase	$ 43,422	39,226
Visa Incorporation
Loss Contingencies [Line Items]
Other company stock owned shares | shares	483,806
Conversion ratio from Class B shares into Class A shares	1.6483
Value of the Class A shares (in usd per share) | $ / shares	$ 114.02
Unredeemed Class A equivalent shares owned	$ 90,900
Mortgage, net | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
GNMA loans, right to repurchase	43,693	36,827
Mortgage, net | Financing Receivables, Equal to Greater than 90 Days Past Due | Residential
Financing Receivable, Recorded Investment, Past Due [Line Items]
GNMA loans, right to repurchase	36,977	33,703
GNMA | Mortgage, net | Financing Receivables, Equal to Greater than 90 Days Past Due | Residential
Commitments and Contingencies Disclosure [Abstract]
GNMA Loans past due by 90 days, but not yet repurchased	$ 12,400	$ 10,900
Real Estate Loans as Part of Loan portfolio [Member]
Loss Contingencies [Line Items]
Concentration risk, percentage	75.00%	76.00%