Tax Credit Investments - Income Statement Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Components of Income Tax Expense:
Affordable housing tax credits and other tax benefits	$ 1,713	$ 1,821
Other tax credit investment credits and tax benefits	2,803	5,485
Total reduction in income tax expense	4,516	7,306
Non-Interest Expenses
Amortization of Tax Credit Investments:
Affordable housing tax credit investment losses	673	986
Affordable housing tax credit investment impairment losses	730	587
Other tax credit investment losses	987	537
Other tax credit investment impairment losses	4,783	3,164
Total amortization of tax credit investments recorded in non-interest expense	$ 7,173	$ 5,274