Accumulated Other Comprehensive Income (Loss) Accumulated Other Comprehensive Income (Loss) (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended			12 Months Ended	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Dec. 31, 2012 Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Accumulated Net Unrealized Investment Gain (Loss) [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Accumulated Net Unrealized Investment Gain (Loss) [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Accumulated Net Unrealized Investment Gain (Loss) [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Dec. 31, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]	Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2012 Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] Reclassification out of Accumulated Other Comprehensive Income [Member]	Sep. 30, 2013 Other comprehensive income loss before reclassifications [Member] Accumulated Net Unrealized Investment Gain (Loss) [Member]	Sep. 30, 2013 Other comprehensive income loss before reclassifications [Member] Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Other income (expense)	$ (4,640)	$ (4,548)	$ (29,525)	$ 13,546							$ 200	$ (300)	$ 4,500	$ (1,100)
Income tax expense	186,105	131,044	410,753	334,213					9,000	2,500	(100)	100	(1,600)	400	100	1,100	0	0	(300)	(1,900)	6,600	1,200
Revenues	1,827,780	1,385,554	4,966,349	4,098,520													(7,300)	12,000	(6,100)	31,000
Net income	$ 487,616	$ 398,400	$ 1,405,035	$ 1,087,906	$ (7,200)	$ 11,800	$ (3,500)	$ 28,400