Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUES:
Net premiums written	$ 6,423,913	$ 6,189,515	$ 5,996,947
Change in net unearned premiums	(130,565)	(148,906)	(252,529)
Net premiums earned	6,293,348	6,040,609	5,744,418
Net investment income	564,163	512,645	600,885
Insurance service fees	138,944	139,440	117,443
Net investment gains:
Net realized gains on investment sales	285,119	125,633	254,852
Other-than-temporary impairments	(18,114)	(33,309)	0
Net investment gains	267,005	92,324	254,852
Revenues from non-insurance businesses	390,348	421,102	410,022
Other income	376	337	1,308
Total revenues	7,654,184	7,206,457	7,128,928
OPERATING COSTS AND EXPENSES:
Losses and loss expenses	3,845,800	3,656,270	3,490,567
Other operating costs and expenses	2,395,619	2,289,750	2,157,456
Expenses from non-insurance businesses	375,431	397,461	400,535
Interest expense	140,896	130,946	128,174
Total operating costs and expenses	6,757,746	6,474,427	6,176,732
Income before income taxes	896,438	732,030	952,196
Income Tax expense	(292,953)	(227,923)	(302,593)
Net income before noncontrolling interests	603,485	504,107	649,603
Noncontrolling interests	(1,569)	(413)	(719)
Net income to common stockholders	$ 601,916	$ 503,694	$ 648,884
NET INCOME PER SHARE:
Basic (dollars per share)	$ 4.91	$ 4.06	$ 5.07
Diluted (dollars per share)	$ 4.68	$ 3.87	$ 4.86