Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017 USD ($) segment trust	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Property, Plant and Equipment [Line Items]
Number of wholly owned trusts | trust	25
Cash and cash equivalents general maturity	90 days
Unallocated allowance maximum amount	5.00%
Restricted equity securities	$ 43,508,000	$ 45,528,000
Impairment charges related to SBA/USDA servicing assets	$ 0	0	$ 0
Number of primary segments | segment	4
2013 Stock Incentive Plan
Property, Plant and Equipment [Line Items]
Share-based compensation arrangement by share-based payment award, award expiration period	10 years
Land and Building
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	39 years
Minimum | 2013 Stock Incentive Plan
Property, Plant and Equipment [Line Items]
Share-based compensation award, vesting period	3 years
Minimum | Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Minimum | Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	3 years
Maximum | 2013 Stock Incentive Plan
Property, Plant and Equipment [Line Items]
Share-based compensation award, vesting period	5 years
Maximum | Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	10 years
Maximum | Software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, useful life	7 years
Investment in Federal Home Loan Bank Stock
Property, Plant and Equipment [Line Items]
Restricted equity securities	$ 42,000,000	$ 44,100,000
Federal home loan bank stock, minimum investment	$ 42,000,000