Tax Credit Investments Tax Credit Investments - Affordable Housing Tax Credit Investments, Other Tax Credit Investments, and Related Unfunded Commitments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Assets
Other Assets:
Affordable housing tax credit investments, net	$ 22,135	$ 29,567
Other tax credit investments, net	42,015	44,763
Total tax credit investments, net	64,150	74,330
Other Liabilities
Other Liabilities:
Unfunded affordable housing tax credit commitments	3,690	4,850
Unfunded other tax credit commitments	15,020	7,276
Total unfunded tax credit commitments	$ 18,710	$ 12,126