Consolidated Statements of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Class A Common Stock	Class B Common Stock	Common Stock Class A Common Stock	Common Stock Class B Common Stock	Surplus	Surplus Class A Common Stock	Surplus Class B Common Stock	Retained Earnings	Retained Earnings Class A Common Stock	Retained Earnings Class B Common Stock	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Class A Common Stock	Accumulated Other Comprehensive Loss Class B Common Stock
Beginning balance at Dec. 31, 2010	$ 1,732,962			$ 8,757	$ 1,678	$ 143,766			$ 1,615,290			$ (36,529)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	195,028			0	0	0			195,028			0
Net current period other comprehensive income	(30,045)			0	0	0			0			(30,045)
Repurchase of common stock shares		(16,785)	(7,602)	(113)	(38)		0	0		(16,672)	(7,564)		0	0
Cash dividends	(12,430)			0	0	0			(12,430)			0
Ending balance at Dec. 31, 2011	1,861,128			8,644	1,640	143,766			1,773,652			(66,574)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	134,348			0	0	0			134,348			0
Net current period other comprehensive income	(15,532)			0	0	0			0			(15,532)
Repurchase of common stock shares		(9,131)	(94,493)	(56)	(607)		0	0		(9,075)	(93,886)		0	0
Cash dividends	(12,313)			0	0	0			(12,313)			0
Ending balance at Dec. 31, 2012	1,864,007			8,588	1,033	143,766			1,792,726			(82,106)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	167,699			0	0	0			167,699			0
Net current period other comprehensive income	56,838			0	0	0			0			56,838
Repurchase of common stock shares		(321)		(2)			0			(319)			0
Cash dividends	(11,548)			0	0	0			(11,548)			0
Ending balance at Dec. 31, 2013	$ 2,076,675			$ 8,586	$ 1,033	$ 143,766			$ 1,948,558			$ (25,268)