Variable Interest Entities (Nonconsolidated Variable Interest Entities) (Detail) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Variable Interest Entity [Line Items]
Carrying Amount		$ 233,925	$ 240,057
Maximum Exposure to Loss		79,837	80,369
Trust Preferred Capital Securities Issuances [Member]
Variable Interest Entity [Line Items]
Carrying Amount		169,788	169,788
Maximum Exposure to Loss		0	0
Community Reinvestment Investments [Member]
Variable Interest Entity [Line Items]
Carrying Amount		10,887	14,360
Maximum Exposure to Loss		12,581	16,054
Restructured loans to commercial clients, outstanding loan balance [Member]
Variable Interest Entity [Line Items]
Carrying Amount	[1]	53,213	49,376
Maximum Exposure to Loss	[1]	67,219	57,782
Restructured loans to commercial clients, related derivative asset [Member]
Variable Interest Entity [Line Items]
Carrying Amount	[1]	37	6,533
Maximum Exposure to Loss	[1]	$ 37	$ 6,533

[1] Excludes personal loans and loans to non-for-profit entities.