Leases (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011
Future minimum payments for leases
Future minimum payments, Operating Leases (As Lessor), 2012	$ 767,878
Future minimum payments, Direct Financing Leases (as Lessor), 2012	89,573
Future minimum payments, Operating Leases (As Lessee), 2012	96,623
Future minimum payments, Operating Leases (As Lessor), 2013	531,363
Future minimum payments, Direct Financing Leases (as Lessor), 2013	77,495
Future minimum payments, Operating Leases (As Lessee), 2013	72,469
Future minimum payments, Operating Leases (As Lessor), 2014	362,674
Future minimum payments, Direct Financing Leases (as Lessor), 2014	66,052
Future minimum payments, Operating Leases (As Lessee), 2014	69,182
Future minimum payments, Operating Leases (As Lessor), 2015	246,185
Future minimum payments, Direct Financing Leases (as Lessor), 2015	52,085
Future minimum payments, Operating Leases (As Lessee), 2015	29,235
Future minimum payments, Operating Leases (As Lessor), 2016	153,067
Future minimum payments, Direct Financing Leases (as Lessor), 2016	38,540
Future minimum payments, Operating Leases (As Lessee), 2016	14,846
Future minimum payments, Operating Leases (As Lessor), Thereafter	120,056
Future minimum payments, Direct Financing Leases (as Lessor), Thereafter	56,207
Future minimum payments, Operating Leases (As Lessee), Thereafter	30,797
Future minimum payments, Operating Leases (As Lessor), Total	2,181,223
Future minimum payments, Direct Financing Leases (As Lessor), Total	379,952
Future minimum payments, Operating Leases (As Lessee), Total	$ 313,152