Short-Term Borrowings and Long-Term Debt - Outstanding Short Term Borrowings and Long Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013	Dec. 31, 2013
Debt Outstanding [Line Items]
Borrowings	$ 5,792		$ 5,794
Short-term borrowings	4,810			5,080
Total long-term debt	454,770			455,216
Other short-term borrowings
Debt Outstanding [Line Items]
Principal value	4,810	[1]
Short-term borrowings	4,810	[1]		5,080	[1]
5.375% Senior Notes
Debt Outstanding [Line Items]
Maturity	Sep. 15, 2020
Principal value	350,000
Senior Notes	348,265			348,209
6.05% Subordinated Notes
Debt Outstanding [Line Items]
Maturity	Jun. 01, 2017	[2]
Principal value	45,964	[2]
Subordinated Notes	51,528	[2]		51,987	[2]
7.0% Junior Subordinated Debentures
Debt Outstanding [Line Items]
Maturity	Oct. 15, 2033
Principal value	50,000
Junior Subordinated Debentures	$ 54,977			$ 55,020

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

[2] ncluded in the carrying value of our 6.05% Subordinated Notes at both March 31, 2014 and December 31, 2013 was an interest rate swap valued at $6.0 million related to hedge accounting associated with the notes.