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	35,495		0	0	0	35,495	0
Net current period other comprehensive income	158		0	0	0	0	158
Repurchase of common stock shares	(1,573)		0	(9)	0	(1,564)	0
Cash dividends	(3,085)		0	0	0	(3,085)	0
Ending balance at Mar. 31, 2012	1,892,123	[1]	8,644	1,631	143,766	1,804,498	(66,416)
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	55,585		0	0	0	55,585	0
Net current period other comprehensive income	2,201		0	0	0	0	2,201
Repurchase of common stock shares	(321)		(2)	0	0	(319)	0
Cash dividends	(2,891)		0	0	0	(2,891)	0
Ending balance at Mar. 31, 2013	$ 1,918,581	[1]	$ 8,586	$ 1,033	$ 143,766	$ 1,845,101	$ (79,905)

[1] Unaudited

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