CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock Member	Additional Paid In Capital Member	Retained Earnings Member	Treasury Stock Member	Accumulated Other Comprehensive Income Member
Total stockholders equity at Dec. 31, 2012	$ 6,910,187	$ 791	$ 1,755,421	$ 3,357,255	$ (312,182)	$ 2,108,902
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	418,837			418,837
Other Comprehensive Income (Loss), Net of Tax	(1,103,295)					(1,103,295)
Dividends to stockholders	(77,642)			(77,642)
Purchase of treasury stock	(269,204)				(269,204)
Reissuance of treasury stock	(56,644)		(22,485)	(38,512)	(72,671)
Total stockholders equity at Dec. 31, 2013	5,935,527	791	1,777,906	3,659,938	(508,715)	1,005,607
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	684,047			684,047
Other Comprehensive Income (Loss), Net of Tax	651,522					651,522
Dividends to stockholders	(87,256)			(87,256)
Purchase of treasury stock	(201,525)				(201,525)
Reissuance of treasury stock	(41,137)		(20,373)	(17,082)	(37,846)
Total stockholders equity at Dec. 31, 2014	7,023,452	791	1,798,279	4,239,647	(672,394)	1,657,129
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net Income (Loss) Attributable to Parent	502,166			502,166
Other Comprehensive Income (Loss), Net of Tax	(948,845)					(948,845)
Dividends to stockholders	(93,381)			(93,381)
Purchase of treasury stock	(384,519)				(384,519)
Reissuance of treasury stock	(36,508)		(17,863)	(28,129)	(46,774)
Total stockholders equity at Dec. 31, 2015	$ 6,135,381	$ 791	$ 1,816,142	$ 4,620,303	$ (1,010,139)	$ 708,284