Income Taxes (Tables)

12 Months Ended

Dec. 31, 2011

Income Taxes [Abstract]

Income Tax Allocation

	Years Ended December 31,
	2011			2010			2009
Income taxes from continuing operations	$	114,225		$	163,800		$	52,140
Stockholders’ equity, tax benefit related to share-based payments, net		(18,593	)		(3,097	)		(842	)
Stockholders’ equity, tax expense related to unrealized gain on held-to-maturity investment portfolio at time of transfer to available-for-sale		—			—			1,835
Stockholders’ equity, tax expense (benefit) related to unrealized gain (loss) on available-for-sale securities		6,340			(476	)		1,369

Current and Deferred tax expense from continuing operations

	Current		Deferred			Total
Year ended December 31, 2011:
U.S. federal	$	98,062	$	9,641		$	107,703
State and local		7,108		(586	)		6,522
	$	105,170	$	9,055		$	114,225
Year ended December 31, 2010:
U.S. federal	$	151,953	$	(2,642	)	$	149,311
State and local		14,109		380			14,489
	$	166,062	$	(2,262	)	$	163,800
Year ended December 31, 2009:
U.S. federal	$	48,532	$	86		$	48,618
State and local		2,790		732			3,522
	$	51,322	$	818		$	52,140

Income tax expense from continuing operations by applying the statutory U.S. federal income tax rate to income before income taxes

	Years Ended December 31,
	2011				2010				2009
	Amount		%		Amount		%		Amount			%
Tax expense at statutory rate	$	108,446		35.0	$	153,010		35.0	$	70,496			35.0
Increase in income taxes resulting from:
State and local income taxes, net of federal income tax effect		4,239		1.4		9,418		2.2		2,549			1.3
Effect of nondeductible expenses and other, net		1,540		0.5		1,372		0.3		1,544			0.7
Decrease in income taxes resulting from:
IRS pre-filing agreement on qui tam settlement		—		—		—		—		(22,449	)		(11.1	)
Total income tax expense	$	114,225		36.9	$	163,800		37.5	$	52,140			25.9

Significant portions of the deferred tax assets and deferred tax liabilities

	December 31,
	2011			2010
Deferred tax assets:
Estimated claims incurred but not reported, a portion of which is deductible as paid for tax purposes	$	5,160		$	4,945
Vacation, bonus, stock compensation and other accruals, deductible as paid for tax purposes		28,273			27,182
Accounts receivable allowances, deductible as written off for tax purposes		9,614			7,532
Start-up costs, deductible in future periods for tax purposes		767			382
Unearned revenue, a portion of which is includible in income as received for tax purposes		—			8,257
2.0% Convertible Senior Notes		558			583
State net operating loss/credit carryforwards, deductible in future periods for tax purposes		648			—
Gross deferred tax assets		45,020			48,881
Deferred tax liabilities:
Goodwill, due to timing differences in book and tax amortization		(6,529	)		(5,500	)
Unrealized gains on investments		(6,717	)		(377	)
Property, equipment and software, due to timing differences in book and tax depreciation		(24,075	)		(20,060	)
Deductible prepaid expenses and other		(2,426	)		(2,274	)
Gross deferred tax liabilities		(39,747	)		(28,211	)
Net deferred tax assets	$	5,273		$	20,670

Summary of the reconciliation of the beginning and ending amount of unrecognized tax benefits

	Amount
Balance at December 31, 2009	$	882
Additions based on tax positions for current year		—
Additions for tax positions of prior years		—
Reductions for tax positions of prior years		(125	)
Settlements		—
Balance at December 31, 2010		757
Additions based on tax positions for current year		—
Additions for tax positions of prior years		—
Reductions for tax positions of prior years		(118	)
Settlements		(639	)
Balance at December 31, 2011	$	—