Income Taxes (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Summary of activities related to unrecognized tax benefits
Balance at the beginning of the period	$ 19,583,000	$ 21,883,000
Additions to tax positions related to the current year	3,489,000	3,752,000
Additions to tax positions related to prior years	59,000	490,000
Subtractions to tax positions related to prior years	(968,000)	(850,000)
Subtractions to tax positions related to settlements	(47,000)	0
Subtractions to tax positions as a result of the lapse of the statute of limitations	(2,650,000)	(5,692,000)
Balance at the end of the period	19,466,000	19,583,000
Unrecognized tax benefits that, if recognized, would reduce annual effective tax rate	17,900,000	19,100,000
Accrued interest related to unrecognized tax benefits	300,000
Expected increase in unrecognized tax benefits during next fiscal year	$ 2,000,000