Fair Value Measurements - Level 3 Assets, Nonrecurring Basis (Details) - Nonrecurring - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 56,829	$ 73,518
Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	54,060	70,619
Other real estate and repossessed assets
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	2,769	2,899
Level 3
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	56,829	73,518
Level 3 | Impaired loans
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Total assets measured at fair value on a nonrecurring basis	$ 54,060	70,619
Level 3 | Impaired loans | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	20.00%
Level 3 | Impaired loans | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	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	$ 2,769	$ 2,899
Level 3 | Other real estate and repossessed assets | Minimum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	20.00%
Level 3 | Other real estate and repossessed assets | Maximum
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount rate	30.00%