Fair Value - Schedule of Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Available for sale securities	$ 1,333,401	$ 1,421,772
Held to maturity securities	2,343,828	2,611,352
Loans, net	12,755,384	12,191,191
Loans held for sale	22,017	24,515
Derivative financial instruments	17,700	15,579
Deposits	15,245,227	15,360,516
Long-term debt	374,991	385,826
Derivative financial instruments	18,458	15,006
Level 1 [Member]
Cash, interest-bearing bank deposits, and federal funds sold	865,297	617,280
Available for sale securities	13,491	14,728
Held to maturity securities		100,316
Loans, net
Loans held for sale
Accrued interest receivable	44,259	42,977
Derivative financial instruments
Deposits
Federal funds purchased	4,225	7,725
Securities sold under agreements to repurchase	644,439	650,235
FHLB borrowings	415,000
Long-term debt
Accrued interest payable	4,090	4,353
Derivative financial instruments
Level 2 [Member]
Cash, interest-bearing bank deposits, and federal funds sold
Available for sale securities	1,319,910	1,407,044
Held to maturity securities	2,355,413	2,476,268
Loans, net	32,996	24,392
Loans held for sale	22,017	24,515
Accrued interest receivable
Derivative financial instruments	17,700	15,579
Deposits
Federal funds purchased
Securities sold under agreements to repurchase
Long-term debt	372,037	385,557
Accrued interest payable
Derivative financial instruments	18,458	15,006
Level 3 [Member]
Cash, interest-bearing bank deposits, and federal funds sold
Available for sale securities
Held to maturity securities
Loans, net	12,635,212	12,023,330
Loans held for sale
Accrued interest receivable
Derivative financial instruments
Deposits	14,938,111	15,352,024
Federal funds purchased
Securities sold under agreements to repurchase
Long-term debt
Accrued interest payable
Derivative financial instruments
Total Fair Value [Member]
Cash, interest-bearing bank deposits, and federal funds sold	865,297	617,280
Available for sale securities	1,333,401	1,421,772
Held to maturity securities	2,355,413	2,576,584
Loans, net	12,668,208	12,047,722
Loans held for sale	22,017	24,515
Accrued interest receivable	44,259	42,977
Derivative financial instruments	17,700	15,579
Deposits	14,938,111	15,352,024
Federal funds purchased	4,225	7,725
Securities sold under agreements to repurchase	644,439	650,235
FHLB borrowings	415,000
Long-term debt	372,037	385,557
Accrued interest payable	4,090	4,353
Derivative financial instruments	18,458	15,006
Carrying Amount [Member]
Cash, interest-bearing bank deposits, and federal funds sold	865,297	617,280
Available for sale securities	1,333,401	1,421,772
Held to maturity securities	2,343,828	2,611,352
Loans, net	12,755,384	12,191,191
Loans held for sale	22,017	24,515
Accrued interest receivable	44,259	42,977
Derivative financial instruments	17,700	15,579
Deposits	15,245,227	15,360,516
Federal funds purchased	4,225	7,725
Securities sold under agreements to repurchase	644,439	650,235
FHLB borrowings	415,000
Long-term debt	374,991	385,826
Accrued interest payable	4,090	4,353
Derivative financial instruments	$ 18,458	$ 15,006

Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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The aggregate of all deposit liabilities held by the entity, including foreign and domestic, interest and noninterest bearing; may include demand deposits, saving deposits, Negotiable Order of Withdrawal (NOW) and time deposits among others.

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Amount of short term borrowing where a bank borrows, at the federal funds rate, from another bank.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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