Supplemental Financial Information Comprehensive Income (Schedule Of Reclassifications Of Recognized Transactions Out Of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net									$ 5,898	$ (404)	$ (352)
Income tax provision									(37,073)	(24,788)	(42,990)
Net income	111,495	105,401	99,806	78,579	59,690	10,173	(21,184)	78,710	395,281	127,389	336,705
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense), net									2,371	394	157
Income tax provision									(776)	(51)	58
Net income									$ 1,595	$ 343	$ 215