Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Treasury Stock
Beginning Balance at Dec. 31, 2013	$ 1,223,502	$ 117	$ 631,667	$ 1,035,198	$ (67,817)	$ (375,663)
Net income	368,707			368,707
Other comprehensive loss, net of tax	(223,691)				(223,691)
Acquisition/return of common stock	1,125,964		(1,096,698)			(29,266)
Issuance of common stock	124,080	3	124,077
Ending Balance at Dec. 31, 2014	2,618,562	120	1,852,442	1,403,905	(291,508)	(346,397)
Net income	362,431			362,431
Other comprehensive loss, net of tax	(279,303)				(279,303)
Acquisition/return of common stock	8,119		0			8,119
Issuance of common stock	136,476	1	136,475
Ending Balance at Dec. 31, 2015	2,830,047	121	1,988,917	1,766,336	(570,811)	(354,516)
Net income	452,385			452,385
Other comprehensive loss, net of tax	(95,592)				(95,592)
Acquisition/return of common stock	187,979					187,979
Issuance of common stock	85,177	0	85,177
Ending Balance at Dec. 31, 2016	$ 3,084,038	$ 121	$ 2,074,094	$ 2,218,721	$ (666,403)	$ (542,495)