Short-term Investments (Gross Gains (Losses) Realized On Sales, Maturities And Other Securities Transactions Related To Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments [Abstract]
Proceeds from sales of available-for-sale investment securities	$ 670,498	$ 211,696	$ 1,028,320	$ 871,696
Gross gains	604	315	1,357	1,530
Gross losses	(68)	(166)	(134)	(553)
Net gains on sales of available-for-sale investment securities	$ 536	$ 149	$ 1,223	$ 977