Debt and Equity Securities (Cost and Estimated Fair Value of Investments in Equity Securities, Classified as Available-For-Sale) (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Equity securities	$ 313,289	$ 358,043
Equity Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	285,673	334,099
Gross unrealized, gains	28,277	26,704
Gross unrealized, losses	(661)	(2,760)
Equity securities	313,289	358,043
Equity Securities | Preferred stocks
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	9,653	9,915
Gross unrealized, gains	1,936	1,567
Gross unrealized, losses	(232)	(397)
Equity securities	11,357	11,085
Equity Securities | Common Stock
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	276,020	324,184
Gross unrealized, gains	26,341	25,137
Gross unrealized, losses	(429)	(2,363)
Equity securities	$ 301,932	$ 346,958