Short-Term Borrowings and Long-Term Debt Outstanding Short Term Borrowings and Long Term Debt (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	0 Months Ended		12 Months Ended			12 Months Ended				12 Months Ended
	Apr. 15, 2011 3.875% Convertible Notes	Dec. 31, 2011 3.875% Convertible Notes	Dec. 31, 2013 5.375% Senior Notes	Dec. 31, 2012 5.375% Senior Notes	Dec. 31, 2011 5.70% Senior Notes	Dec. 31, 2013 6.05% Subordinated Notes	Dec. 31, 2012 6.05% Subordinated Notes	Dec. 31, 2013 6.05% Subordinated Notes Interest rate swaps	Dec. 31, 2012 6.05% Subordinated Notes Interest rate swaps	Dec. 31, 2013 7.0% Junior Subordinated Debentures	Dec. 31, 2012 7.0% Junior Subordinated Debentures
Debt Outstanding [Line Items]
Stated interest rate		3.875%	5.375%	5.375%	5.70%	6.05%	6.05%			7.00%	7.00%
Fair value of the interest rate swap associated with the notes						$ 6,500	$ 9,000	$ 6,500	$ 9,000
Maturity	Apr. 15, 2011		Sep. 15, 2020	Sep. 15, 2020		Jun. 01, 2017				Oct. 15, 2033	Oct. 15, 2033