Commitments and Contingencies - Operating Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Commitments under operating leases [Abstract]
2013	$ 8,752,000
2014	7,827,000
2015	7,772,000
2016	7,857,000
2017	7,517,000
Thereafter	52,520,000
Total	92,245,000
Rent expense under operating leases [Abstract]
Rent expense under operating leases	8,029,000	7,790,000	7,636,000
Rent charges for utilities, real estate taxes, and operating expense	10,900,000	9,300,000	10,300,000
Facilities
Commitments under operating leases [Abstract]
2013	7,502,000
2014	7,554,000
2015	7,698,000
2016	7,857,000
2017	7,517,000
Thereafter	52,520,000
Total	90,648,000
Rent expense under operating leases [Abstract]
Rent expense under operating leases	7,428,000	7,191,000	7,301,000
Equipment
Commitments under operating leases [Abstract]
2013	1,250,000
2014	273,000
2015	74,000
Total	1,597,000
Rent expense under operating leases [Abstract]
Rent expense under operating leases	601,000	599,000	335,000
Tarrytown Lease
Operating Leases [Abstract]
Number of new buildings leased	2
Number of renewal options to extend the term of the lease	3
Lease extension term	5 years
Lease renewal escalation percentage	2.50%
Letter of credit amount outstanding in connection with lease	3,400,000	3,400,000
Cash and marketable debt securities collateral	$ 3,700,000	$ 3,600,000