STATEMENTS OF SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Class A	Class B	Common stock Class A	Common stock Class B	Additional paid-in-capital	Accumulated other comprehensive income (loss)	Retained earnings	Retained earnings Class A	Retained earnings Class B	Treasury stock	Deferred compensation
Balance, end of year at Dec. 31, 2014	$ 703,134			$ 1,992	$ 178	$ 16,317	$ (117,701)	$ 1,948,438			$ (1,146,090)
Increase (decrease) in shareholders' equity
Net income	174,678							174,678
Other comprehensive income (loss)	20,837						20,837
Dividends declared		$ (128,082)	$ (1,058)						$ (128,082)	$ (1,058)
Net purchase of treasury stock	(6)					(6)					0
Deferred compensation	0										(9,018)	$ 9,018
Balance, end of year at Dec. 31, 2015	769,503			1,992	178	16,311	(96,864)	1,993,976			(1,155,108)	9,018
Increase (decrease) in shareholders' equity
Net income	210,366							210,366
Other comprehensive income (loss)	(24,517)						(24,517)
Dividends declared		(137,297)	(1,134)						(137,297)	(1,134)
Net purchase of treasury stock	(11)					(11)					0
Deferred compensation	0										(738)	738
Balance, end of year at Dec. 31, 2016	816,910			1,992	178	16,300	(121,381)	2,065,911			(1,155,846)	9,756
Increase (decrease) in shareholders' equity
Net income	196,999							196,999
Other comprehensive income (loss)	(8,295)						(8,295)
Dividends declared		$ (147,225)	$ (1,215)						$ (147,225)	$ (1,215)
Net purchase of treasury stock	170					170					0
Deferred compensation	0										(1,177)	1,177
Rabbi trust distribution	0										1,355	(1,355)
AOCI reclassification	0						(26,383)	26,383
Balance, end of year at Dec. 31, 2017	$ 857,344			$ 1,992	$ 178	$ 16,470	$ (156,059)	$ 2,140,853			$ (1,155,668)	$ 9,578