Income Taxes (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Operating Loss Carryforwards [Line Items]
Income before provision for income taxes	$ 30,000	$ 17,536	$ 110,868	$ 66,998
Income tax expense using estimated annual effective income tax rate	11,920	6,973	44,051	26,623
Impact of discrete item, net	0		464	0
Changes in effective tax rates	1,401	691	0	0
Reduction of valuation allowance	(870)	0	(870)	(500)
Reversal of unrecognized tax benefits	0	(1,035)	0	(1,193)
Income tax expense	12,451	6,629	43,645	24,930
Income tax benefit	$ 870	$ 0	$ 870	$ 500