Consolidated Statements of Income (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
REVENUES:
Net premiums written	$ 5,500,173	$ 4,898,539	$ 4,357,368
Change in net unearned premiums	(273,636)	(225,023)	(196,501)
Net premiums earned	5,226,537	4,673,516	4,160,867
Net investment income	544,291	586,763	526,351
Insurance service fees	107,513	103,133	92,843
Net investment gains:
Net realized gains on investment sales	127,586	201,451	125,881
Other-than-temporary impairments and change in valuation allowance	(6,042)	9,014	(400)
Net investment gains	121,544	210,465	125,481
Revenues from wholly-owned investees	407,623	247,113	248,678
Other income	1,026	2,564	1,764
Total revenues	6,408,534	5,823,554	5,155,984
OPERATING COSTS AND EXPENSES:
Losses and loss expenses	3,197,024	2,948,479	2,658,365
Other operating costs and expenses	2,000,684	1,799,623	1,626,526
Expenses from wholly-owned investees	388,761	247,222	245,495
Interest expense	123,177	126,302	112,512
Total operating costs and expenses	5,709,646	5,121,626	4,642,898
Income before income taxes	698,888	701,928	513,086
Income tax expense	(193,587)	(191,285)	(121,945)
Net income before noncontrolling interests	505,301	510,643	391,141
Noncontrolling interests	(5,376)	(51)	70
Net income to common stockholders	$ 499,925	$ 510,592	$ 391,211
NET INCOME PER SHARE:
Basic (dollars per share)	$ 3.69	$ 3.72	$ 2.80
Diluted (dollars per share)	$ 3.55	$ 3.56	$ 2.69