Commitments and Contingencies, Leases (Details) (USD $)	12 Months Ended			24 Months Ended
	Dec. 31, 2011 Percent	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2010
Commitments under operating leases [Abstract]
2012	$ 7,260,000
2013	7,562,000
2014	7,463,000
2015	7,583,000
2016	7,738,000
Thereafter	59,631,000
Total	97,237,000
Rent expense under operating leases [Abstract]
Rent expense	7,790,000	7,636,000	8,117,000
Rental charges for utilities, real estate taxes, and operating expense	9,300,000	10,300,000	8,400,000
Capital leases [Abstract]
Marketable debt securities collateral	3,300,000	3,500,000		3,500,000
Commitments under capital leases [Abstract]
Capital lease obligations	2,500,000	2,800,000		2,800,000
Facility lease obligations [Abstract]
Interest expense in connection with facility lease obligation	15,600,000
Commitments under facility leases [Abstract]
2012	15,672,000
2013	17,462,000
2014	17,833,000
2015	18,214,000
2016	18,604,000
Thereafter	152,939,000
Total	240,724,000
Buildings A and B [Member]
Facility lease obligations [Abstract]
Capitalized costs of constructing the new facility		58,400,000		58,400,000
Reimbursements recognized as additional facility lease obligation				56,900,000
Imputed interest rate applicable to the facility lease obligation (in hundredths)	11.00%
Interest expense in connection with facility lease obligation		9,100,000	2,300,000
Facility lease obligation	113,000,000	113,700,000		113,700,000
Commitments under facility leases [Abstract]
2012	12,847,000
2013	13,092,000
2014	13,343,000
2015	13,600,000
2016	13,864,000
Thereafter	113,040,000
Total	179,786,000
Building C [Member]
Facility lease obligations [Abstract]
Capitalized costs of constructing the new facility		27,800,000		27,800,000
Reimbursements recognized as additional facility lease obligation		14,200,000
Imputed interest rate applicable to the facility lease obligation (in hundredths)	9.00%
Facility lease obligation	47,500,000	46,400,000		46,400,000
Commitments under facility leases [Abstract]
2012	2,825,000
2013	4,370,000
2014	4,490,000
2015	4,614,000
2016	4,740,000
Thereafter	39,899,000
Total	60,938,000
Facilities [Member]
Commitments under operating leases [Abstract]
2012	6,072,000
2013	7,304,000
2014	7,428,000
2015	7,583,000
2016	7,738,000
Thereafter	59,631,000
Total	95,756,000
Rent expense under operating leases [Abstract]
Rent expense	7,191,000	7,301,000	7,722,000
Equipment [Member]
Commitments under operating leases [Abstract]
2012	1,188,000
2013	258,000
2014	35,000
Total	1,481,000
Rent expense under operating leases [Abstract]
Rent expense	599,000	335,000	395,000
Commitments under capital leases [Abstract]
2012	1,394,000
2013	1,254,000
2014	130,000
Total	2,778,000
Less: amount representing interest	(272,000)
Total	2,506,000
Tarrytown Lease [Member]
Operating leases [Abstract]
Number of new buildings leased	2
Description of leasing arrangement	expire in June 2024 and contains three renewal options to extend the term of the lease by five years each, escalations at 2.5% per annum
Letter of credit amount outstanding in connection with lease	3,400,000	3,400,000		3,400,000
Cash and marketable debt securities collateral	$ 3,600,000	$ 3,600,000		$ 3,600,000