Consolidated Statements of Income (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Revenues:
Premium	$ 6,301,425	$ 5,783,458	$ 5,158,989
Investment income and other	16,969	22,843	29,081
Total revenues	6,318,394	5,806,301	5,188,070
Expenses:
Health benefits	5,272,259	4,722,106	4,407,273
Selling, general and administrative	514,804	452,069	394,089
Premium tax	163,566	143,896	134,277
Depreciation and amortization	37,369	35,048	34,746
Interest	20,550	16,011	16,266
Total expenses	6,008,548	5,369,130	4,986,651
Income before income taxes	309,846	437,171	201,419
Income tax expense	114,225	163,800	52,140
Net income	$ 195,621	$ 273,371	$ 149,279
Net income per share:
Basic net income per share	$ 4.10	$ 5.52	$ 2.89
Weighted average number of common shares outstanding	47,731,265	49,522,202	51,647,267
Diluted net income per share	$ 3.82	$ 5.40	$ 2.85
Weighted average number of common shares and dilutive potential common shares outstanding	51,163,108	50,608,008	52,309,268