Tax Credit Investments Tax Credit Investments - Affordable Housing Tax Credit Investments and Other Tax Credit Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Schedule of Equity Method Investments [Line Items]
Affordable housing tax credits and other tax benefits	$ 1,065	$ 1,383	$ 2,130	$ 3,114
Other tax credit investment credits and tax benefits	3,268	4,903	6,536	8,521
Total reduction in income tax expense	4,333	6,286	8,666	11,635
Non-Interest Expenses [Member]
Schedule of Equity Method Investments [Line Items]
Affordable housing tax credit investment losses	775	296	1,359	973
Affordable housing tax credit investment impairment losses	60	40	200	528
Other tax credit investment losses	594	493	668	790
Other tax credit investment impairment losses	6,217	3,682	12,683	6,716
Total amortization of tax credit investments recorded in non-interest expense	$ 7,646	$ 4,511	$ 14,910	$ 9,007