Goodwill and Other Intangible Assets - Total Amortizing Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,064,727	$ 933,062
Accumulated Amortization	924,459	898,035
Net Carrying Amount	140,268	35,027
Core Deposit [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	887,459	755,794
Accumulated Amortization	750,624	730,188
Net Carrying Amount	136,835	25,606
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	177,268	177,268
Accumulated Amortization	173,835	167,847
Net Carrying Amount	$ 3,433	$ 9,421