Consolidated Statements of Changes In Shareholders' Equity - USD ($) $ in Thousands	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	Retained Earnings	Retained Earnings Class A Common Stock	Retained Earnings Class B Common Stock	Accumulated Other Comprehensive (Loss) Income	Financial Instruments ASU cumulative effect adjustment Retained Earnings	Financial Instruments ASU cumulative effect adjustment Accumulated Other Comprehensive (Loss) Income	Income tax ASU cumulative effect adjustment Retained Earnings	Income tax ASU cumulative effect adjustment Accumulated Other Comprehensive (Loss) Income
Shareholders' equity	$ 3,334,064			$ 11,005	$ 1,005	$ 658,918		$ 2,785,430			$ (122,294)
Net income	100,231							100,231
Other comprehensive income (loss), net of tax	(57,978)										(57,978)
Cash dividends		$ (3,851)	$ (352)						$ (3,851)	$ (352)
Cumulative effect of new accounting principle in period of adoption												$ 18,715	$ (18,715)	$ 31,336	$ (31,336)
Shareholders' equity	3,372,114			11,005	1,005	658,918		2,931,509			(230,323)
Shareholders' equity	3,488,954			10,623	1,005	493,962		3,218,551			(235,187)
Net income	111,359							111,359
Other comprehensive income (loss), net of tax	28,327
Stock repurchased during period	(100,700)	(100,756)		(243)			$ (100,513)
Cash dividends		$ (4,173)	$ (402)						$ (4,173)	$ (402)
Shareholders' equity	$ 3,523,309			$ 10,380	$ 1,005	$ 393,449		$ 3,325,335			$ (206,860)