Fair Value Measurements (Level 3 Assets Measured on a Nonrecurring Basis) (Details) - Nonrecurring - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 73,518	$ 63,572
Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis		62,184
Other real estate and repossessed assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,899	1,386
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	73,518	63,572
Level 3 | Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 70,619	62,184
Level 3 | Impaired loans | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	20.00%
Level 3 | Impaired loans | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	30.00%
Level 3 | Other real estate and repossessed assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 2,899	$ 1,386
Level 3 | Other real estate and repossessed assets | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	20.00%
Level 3 | Other real estate and repossessed assets | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	30.00%
Level 3 | Loan Servicing Rights | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	10.00%
Prepayment speed (as a percent)	9.00%
Level 3 | Loan Servicing Rights | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate (as a percent)	11.00%
Prepayment speed (as a percent)	18.00%