Short-Term Borrowings and Long-Term Debt Outstanding Short Term Borrowings and Long Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Sep. 30, 2010
Debt Outstanding [Line Items]
Short-term borrowings	$ 5,080		$ 166,110
Total long-term debt	455,216		457,762
Federal Funds Purchased
Debt Outstanding [Line Items]
Principal value	0
Short-term borrowings	0		160,000
Other short-term borrowings
Debt Outstanding [Line Items]
Principal value	5,080	[1]
Short-term borrowings	5,080	[1]	6,110	[1]
5.375% Senior Notes
Debt Outstanding [Line Items]
Maturity	Sep. 15, 2020		Sep. 15, 2020
Principal value	350,000				350,000
Senior Notes	348,209		347,995
6.05% Subordinated Notes
Debt Outstanding [Line Items]
Maturity	Jun. 01, 2017
Principal value	45,964	[2]
Subordinated Notes	51,987	[2]	54,571	[2]
7.0% Junior Subordinated Debentures
Debt Outstanding [Line Items]
Maturity	Oct. 15, 2033		Oct. 15, 2033
Principal value	50,000
Junior Subordinated Debentures	$ 55,020		$ 55,196

[1] Represents cash collateral received from our counterparty for our interest rate swap agreement related to our 6.05% Subordinated Notes.

[2] At December 31, 2013 and 2012, included in the carrying value of our 6.05% Subordinated Notes were $6 million and $9 million, respectively, related to hedge accounting associated with the notes.