Income Taxes (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Income Taxes
Current	$ 46,389	$ 38,336	$ 72,291	$ 72,324
Deferred	(13,102)	10,461	(5,132)	35,349
Total income tax provision	33,287	48,797	67,159	107,673
Reconciliation between the statutory federal income tax rate and the effective federal income tax rate from continuing operations
Statutory federal income tax rate (as a percent)			35.00%	35.00%
Income tax effect of investment income not subject to federal tax (as a percent)			(2.70%)	(2.20%)
Income tax effect of tax credits (as a percent)			(1.40%)	(1.30%)
Income tax effect of state income taxes, net of federal benefit (as a percent)			2.00%	1.20%
Income tax effect of prior year income tax adjustment (as a percent)			(0.80%)	3.80%
Income tax effect of other, net (as a percent)			1.20%	0.10%
Effective federal income tax rate from continuing operations (as a percent)			33.30%	36.60%
Increase in unrecognized tax benefits			12,965	6,498
Anticipated additional increase in unrecognized tax benefits, low end of range	7,000		7,000
Anticipated additional increase in unrecognized tax benefits, high end of range	$ 9,000		$ 9,000