Consolidated Statements of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total		Common Stock Class A Common Stock	Common Stock Class B Common Stock	Surplus	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning 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	73,078		0	0	0	73,078	0
Net current period other comprehensive income	4,167		0	0	0	0	4,167
Repurchase of common stock shares	(2,414)		0	(13)	0	(2,401)	0
Cash dividends	(6,169)		0	0	0	(6,169)	0
Ending balance at Jun. 30, 2012	1,929,790	[1]	8,644	1,627	143,766	1,838,160	(62,407)
Beginning balance at Dec. 31, 2012	1,864,007	[2]	8,588	1,033	143,766	1,792,726	(82,106)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	99,491		0	0	0	99,491	0
Net current period other comprehensive income	(18,070)		0	0	0	0	(18,070)
Repurchase of common stock shares	(321)		(2)	0	0	(319)	0
Cash dividends	(5,777)		0	0	0	(5,777)	0
Ending balance at Jun. 30, 2013	$ 1,939,330	[1]	$ 8,586	$ 1,033	$ 143,766	$ 1,886,121	$ (100,176)

[1] Unaudited

[2] Derived from 2012 Annual Report on Form 10-K.