Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 2.35% senior notes due September 2016	Sep. 12, 2013 2.35% senior notes due September 2016	Sep. 30, 2013 6.15% senior notes due February 2018	Dec. 31, 2012 6.15% senior notes due February 2018	Sep. 30, 2013 9.25% senior notes due January 2019	Dec. 31, 2012 9.25% senior notes due January 2019	Sep. 30, 2013 5.00% senior notes due September 2020	Dec. 31, 2012 5.00% senior notes due September 2020	Sep. 30, 2013 4.625% senior notes due September 2021	Dec. 31, 2012 4.625% senior notes due September 2021	Sep. 30, 2013 5.10% senior notes due September 2023	Sep. 12, 2013 5.10% senior notes due September 2023	Sep. 30, 2013 Revolving Credit Facility	Dec. 31, 2012 Revolving Credit Facility	Sep. 30, 2013 Commercial paper	Sep. 30, 2013 Other	Dec. 31, 2012 Other
Fair Value of Financial Instruments
Carrying Value	$ 4,116,656	$ 4,448,888	$ 349,803		$ 969,623	$ 968,708	$ 339,607	$ 1,125,000	$ 697,871	$ 697,648	$ 698,087	$ 697,907	$ 348,733		$ 300,000	$ 890,000	$ 332,250	$ 11,494	$ 437
Fair Value	4,392,882	5,142,918	353,959		1,097,743	1,164,813	421,952	1,492,819	732,319	770,707	717,374	755,517	356,041		300,000	890,000	332,250	11,494	437
Subsidiary preferred stock, carrying value	69,188	69,188
Subsidiary preferred stock, fair value	69,750	68,625
Interest rate on senior notes due (as a percent)			2.35%	2.35%	6.15%		9.25%		5.00%		4.625%		5.10%	2.35%
Securities available-for-sale	96,015	200,577
Trading equity securities, fair value		$ 52,705