Tax Credit Investments - Income Statement Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Components of Income Tax Expense:
Affordable housing tax credits and other tax benefits	$ 1,666	$ 1,761	$ 5,087	$ 5,011
Other tax credit investment credits and tax benefits	1,902	5,817	6,863	16,982
Total reduction in income tax expense	3,568	7,578	11,950	21,993
Non-Interest Expenses
Amortization of Tax Credit Investments:
Affordable housing tax credit investment losses	530	708	1,796	1,375
Affordable housing tax credit investment impairment losses	857	558	2,381	1,660
Other tax credit investment losses	1,093	1,103	4,589	2,893
Other tax credit investment impairment losses	1,905	3,043	7,655	9,228
Total amortization of tax credit investments recorded in non-interest expense	$ 4,385	$ 5,412	$ 16,421	$ 15,156