Goodwill and Other Intangible Assets - Total Amortizing Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 1,064,727	$ 1,064,727
Accumulated Amortization	967,072	924,459
Net Carrying Amount	97,655	140,268
Core Deposit [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	887,459	887,459
Accumulated Amortization	789,988	750,624
Net Carrying Amount	97,471	136,835
Other [Member]
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Amount	177,268	177,268
Accumulated Amortization	177,084	173,835
Net Carrying Amount	$ 184	$ 3,433