Consolidated Statements of Changes in Shareholders' Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Capital In Excess of Par Value	Accumulated Other Comprehensive Income	Retained Earnings [Member]
Beginning balances at Dec. 31, 2010
Comprehensive income:
Net income	$ 195,867	$ 0	$ 0	$ 0	$ 195,867
Other comprehensive income, net of tax	25,877	0	0	25,877	0
Total comprehensive income	221,744
Activity in employee compensation plans	14,656	48	14,608	0	0
Ending balances at Dec. 31, 2011	1,947,017	9,541	408,109	19,026	1,510,341
Comprehensive income:
Net income	23,176	0	0	0	23,176
Other comprehensive income, net of tax	(11,439)	0	0	(11,439)	0
Total comprehensive income	11,737
Activity in employee compensation plans	15,547	53	15,494	0	0
Ending balances at Dec. 31, 2012	1,974,301	9,594	423,603	7,587	1,533,517
Comprehensive income:
Net income	184,746	0	0	0	184,746
Other comprehensive income, net of tax	(7,587)	0	0	(7,587)	0
Total comprehensive income	177,159
Activity in employee compensation plans	21,932	65	21,867	0	0
Ending balances at Dec. 31, 2013	$ 2,173,392	$ 9,659	$ 445,470	$ 0	$ 1,718,263