Outstanding Short Term Borrowings and Long Term Debt (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012		Dec. 31, 2011
Debt Outstanding [Line Items]
Short-term borrowings	$ 5,880
Other long-term debt			1,439	[1]
Total long-term debt	458,232		603,648
Other short-term borrowings
Debt Outstanding [Line Items]
Principal value	5,880	[2]
Short-term borrowings	5,880	[2]
5.375% Senior Notes
Debt Outstanding [Line Items]
Maturity	Sep. 15, 2020
Principal value	350,000
Senior Notes	347,893		347,793
5.70% Senior Notes
Debt Outstanding [Line Items]
Maturity	Jun. 01, 2012	[3]
Senior Notes			143,969	[3],[4]
6.05% Subordinated Notes
Debt Outstanding [Line Items]
Maturity	Jun. 01, 2017	[5]
Principal value	45,964	[5]
Subordinated Notes	55,054	[5],[6]	55,075	[5],[6]
7.0% Junior Subordinated Debentures
Debt Outstanding [Line Items]
Maturity	Oct. 15, 2033
Principal value	50,000
Junior Subordinated Debentures	$ 55,285		$ 55,372

[1] Represents long-term notes payable related to one of our debt fund investments. The last payment related to the notes was made in April 2012.

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

[3] At December 31, 2011, included in the carrying value of our 5.70% Senior Notes was $2.6 million related to the fair value of the interest rate swap associated with the notes.

[4] At December 31, 2011, included in the carrying value and estimated fair value of our 5.70% Senior Notes was $2.6 million related to the fair value of the interest rate swap associated with the notes.

[5] At June 30, 2012 and December 31, 2011, included in the carrying value of our 6.05% Subordinated Notes were $9.3 million and $8.8 million, respectively, related to the fair value of the interest rate swap associated with the notes.

[6] At June 30, 2012 and December 31, 2011, included in the carrying value and estimated fair value of our 6.05% Subordinated Notes was $9.3 million and $8.8 million, respectively, related to the fair value of the interest rate swap associated with the notes.