Tax Credit Investments - Income Statement Disclosures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Components of Income Tax Expense:
Affordable housing tax credits and other tax benefits	$ 1,708	$ 1,429	$ 3,421	$ 3,250
Other tax credit investment credits and tax benefits	2,158	5,680	4,961	11,165
Total reduction in income tax expense	3,866	7,109	8,382	14,415
Non-Interest Expenses
Amortization of Tax Credit Investments:
Affordable housing tax credit investment losses	593	(319)	1,266	667
Affordable housing tax credit investment impairment losses	794	515	1,524	1,102
Other tax credit investment losses	2,509	1,253	3,496	1,790
Other tax credit investment impairment losses	967	3,021	5,750	6,185
Total amortization of tax credit investments recorded in non-interest expense	$ 4,863	$ 4,470	$ 12,036	$ 9,744