Direct Financing Leases and Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Direct financing leases, net	$ 364,847	$ 333,152
Investments held in Rabbi Trusts	61,425	48,451
Lease incentives	14,857	15,741
Insurance receivables	15,545	18,402
Start-up costs	13,750	7,422
Prepaid pension asset	58,708	14,049
Lease origination costs	9,387	9,227
Deferred tax asset	6,736	9,009
Other	14,294	16,831
Total	559,549	472,284
Cash and cash equivalents | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments held in Rabbi Trusts	4,956	5,391
U.S. equity mutual funds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments held in Rabbi Trusts	39,958	30,229
Foreign equity mutual funds | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments held in Rabbi Trusts	8,001	5,232
Common collective trusts | Fair Value, Measurements, Recurring | Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments held in Rabbi Trusts	$ 8,510	$ 7,599