Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
REVENUES:
Net premiums written	$ 5,996,947	$ 5,500,173	$ 4,898,539
Change in net unearned premiums	(252,529)	(273,636)	(225,023)
Net premiums earned	5,744,418	5,226,537	4,673,516
Net investment income	600,885	544,291	586,763
Insurance service fees	117,443	107,513	103,133
Net investment gains:
Net realized gains on investment sales	254,852	127,586	201,451
Other-than-temporary impairments and change in valuation allowance	0	(6,042)	9,014
Net investment gains	254,852	121,544	210,465
Revenues from wholly-owned investees	410,022	407,623	247,113
Other income	1,308	1,026	2,564
Total revenues	7,128,928	6,408,534	5,823,554
OPERATING COSTS AND EXPENSES:
Losses and loss expenses	3,490,567	3,197,024	2,948,479
Other operating costs and expenses	2,157,456	2,000,684	1,799,623
Expenses from wholly-owned investees	400,535	388,761	247,222
Interest expense	128,174	123,177	126,302
Total operating costs and expenses	6,176,732	5,709,646	5,121,626
Income before income taxes	952,196	698,888	701,928
Income Tax expense	(302,593)	(193,587)	(191,285)
Net income before noncontrolling interests	649,603	505,301	510,643
Noncontrolling interests	(719)	(5,376)	(51)
Net income to common stockholders	$ 648,884	$ 499,925	$ 510,592
NET INCOME PER SHARE:
Basic (dollars per share)	$ 5.07	$ 3.69	$ 3.72
Diluted (dollars per share)	$ 4.86	$ 3.55	$ 3.56