Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011 leases
Operating lease
Number of leases (leases)			2
Future minimum commitments under facility leases commitments with terms of more than one year
2014	$ 119,301,000
2015	116,487,000
2016	101,519,000
2017	100,080,000
2018	86,673,000
Thereafter	828,142,000
Total minimum lease payments	1,352,202,000
Future minimum sublease income
2014	(8,546,000)
2015	(3,996,000)
2016	0
2017	0
2018	0
Thereafter	0
Total minimum lease payments	(12,542,000)
Rental expense	57,700,000	57,100,000	49,400,000
Fan Pier Leases
Future minimum commitments under facility leases commitments with terms of more than one year
2014	67,206,000
2015	67,206,000
2016	67,206,000
2017	67,206,000
2018	67,206,000
Thereafter	752,798,000
Total minimum lease payments	1,088,828,000
Kendall Square Lease
Operating lease
Optional term of lease agreement (in years)			10 years
Office space used for operation (in square feet)	120,000
Future minimum commitments under facility leases commitments with terms of more than one year
2014	19,879,000
2015	19,879,000
2016	19,879,000
2017	19,879,000
2018	6,626,000
Thereafter	0
Total minimum lease payments	86,142,000
Other Operating Leases
Future minimum commitments under facility leases commitments with terms of more than one year
2014	40,762,000
2015	33,398,000
2016	14,434,000
2017	12,995,000
2018	12,841,000
Thereafter	75,344,000
Total minimum lease payments	$ 189,774,000
Minimum
Future minimum sublease income
Effective interest rate (percentage)	2.00%
Maximum
Future minimum sublease income
Effective interest rate (percentage)	7.00%