Quarterly Results of Operations (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 2,697,413	$ 2,716,588	$ 2,833,020	$ 2,657,173	$ 2,736,794	$ 2,389,815	$ 2,590,642	$ 2,601,102	$ 10,904,194	$ 10,318,353	$ 9,840,911
Total benefits and expenses	2,420,670	2,484,773	2,532,485	2,457,733	2,507,304	2,188,120	2,665,400	2,322,275	9,895,661	9,683,099	8,921,688
Income before income taxes	276,743	231,815	300,535	199,440	229,490	201,695	(74,758)	278,827	1,008,533	635,254	919,223
Net Income (Loss) Attributable to Parent	$ 191,091	$ 157,996	$ 198,296	$ 136,664	$ 144,959	$ 137,955	$ (49,612)	$ 185,535	$ 684,047	$ 418,837	$ 631,893
Basic earnings per share:
Earnings Per Share, Basic (in dollars per share)	$ 2.78	$ 2.30	$ 2.87	$ 1.94	$ 2.05	$ 1.95	$ (0.69)	$ 2.51	$ 9.88	$ 5.82	$ 8.57
Earnings Per Share, Diluted (in dollars per share)	$ 2.75	$ 2.28	$ 2.84	$ 1.92	$ 2.03	$ 1.93	$ (0.69)	$ 2.49	$ 9.78	$ 5.78	$ 8.52