Investments (Amortized Cost, Gross Unrealized Gains And Losses And Fair Value Of Investment Securities Available-For-Sale) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 813,381	$ 545,023
Gross Unrealized Gains	3,600	1,947
Gross Unrealized Losses	(1,189)	(942)
Fair Value	815,792	546,028
U.S. Treasury And Agency Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	460,087	339,982
Gross Unrealized Gains	2,192	994
Gross Unrealized Losses	(330)	(592)
Fair Value	461,949	340,384
Corporate And Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	198,644	122,137
Gross Unrealized Gains	955	835
Gross Unrealized Losses	(585)	(63)
Fair Value	199,014	122,909
Asset-Backed Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	97,612	33,258
Gross Unrealized Gains	200	33
Gross Unrealized Losses	(151)	(137)
Fair Value	97,661	33,154
Municipal Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	44,616	41,802
Gross Unrealized Gains	84	2
Gross Unrealized Losses	(121)	(149)
Fair Value	44,579	41,655
Foreign Government Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,422	7,844
Gross Unrealized Gains	169	83
Gross Unrealized Losses	(2)	(1)
Fair Value	$ 12,589	$ 7,926

Investments in debt and equity securities which are categorized neither as trading securities nor held-to-maturity securities and which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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+ Details