Consolidated Statements of Changes In Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total		Class A Common Stock [Member]	Class B Common Stock [Member]	Common Stock [Member] Class A Common Stock [Member]	Common Stock [Member] Class B Common Stock [Member]	Surplus [Member]	Surplus [Member] Class B Common Stock [Member]	Retained Earnings [Member]	Retained Earnings [Member] Class B Common Stock [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Other Comprehensive Income (Loss) [Member] Class B Common Stock [Member]
Balance at Dec. 31, 2010	$ 1,732,962				$ 8,757	$ 1,678	$ 143,766		$ 1,615,290		$ (36,529)
Comprehensive income:
Net income	61,760				0	0	0		61,760		0
Other comprehensive income, net of tax	(3,378)				0	0	0		0		(3,378)
Total comprehensive income	58,382
Cash dividends	(3,130)				0	0	0		(3,130)		0
Balance at Mar. 31, 2011	1,788,214	[1]			8,757	1,678	143,766		1,673,920		(39,907)
Balance at Dec. 31, 2011	1,861,128	[2]			8,644	1,640	143,766		1,773,652		(66,574)
Comprehensive income:
Net income	35,495				0	0	0		35,495		0
Other comprehensive income, net of tax	158				0	0	0		0		158
Total comprehensive income	35,653
Repurchase of 8,388 shares of Class B common stock			0	(1,573)		(9)		0		(1,564)		0
Cash dividends	(3,085)				0	0	0		(3,085)		0
Balance at Mar. 31, 2012	$ 1,892,123	[1]			$ 8,644	$ 1,631	$ 143,766		$ 1,804,498		$ (66,416)

[1] Unaudited

[2] Derived from 2011 Annual Report on Form 10-K.