Leases (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Future minimum payments for leases
Future minimum payments, Operating Leases (As Lessor), 2013	$ 823,369
Future minimum payments, Direct Financing Leases (as Lessor), 2013	107,890
Future minimum payments, Operating Leases (As Lessee), 2013	106,688
Future minimum payments, Operating Leases (As Lessor), 2014	620,533
Future minimum payments, Direct Financing Leases (as Lessor), 2014	87,459
Future minimum payments, Operating Leases (As Lessee), 2014	96,402
Future minimum payments, Operating Leases (As Lessor), 2015	475,226
Future minimum payments, Direct Financing Leases (as Lessor), 2015	73,507
Future minimum payments, Operating Leases (As Lessee), 2015	54,414
Future minimum payments, Operating Leases (As Lessor), 2016	348,897
Future minimum payments, Direct Financing Leases (as Lessor), 2016	60,254
Future minimum payments, Operating Leases (As Lessee), 2016	34,261
Future minimum payments, Operating Leases (As Lessor), 2017	230,016
Future minimum payments, Direct Financing Leases (as Lessor), 2017	40,109
Future minimum payments, Operating Leases (As Lessee), 2017	21,365
Future minimum payments, Operating Leases (As Lessor), Thereafter	172,756
Future minimum payments, Direct Financing Leases (as Lessor), Thereafter	58,923
Future minimum payments, Operating Leases (As Lessee), Thereafter	58,765
Future minimum payments, Operating Leases (As Lessor), Total	2,670,797
Future minimum payments, Direct Financing Leases (As Lessor), Total	428,142
Future minimum payments, Operating Leases (As Lessee), Total	$ 371,895