Fair Value Measurements (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Assets and liabilities measured at fair value on a recurring basis
Total assets at fair value	$ 40,191	$ 32,833
Total liabilities at fair value	14,613
Direct Financing Leases and Other Assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	19,500	17,404
Interest rate swaps, assets	16,654	15,429
Direct Financing Leases and Other Assets [Member] | Fair Value, Inputs, Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	19,500	17,404
Interest rate swaps, assets	0	0
Direct Financing Leases and Other Assets [Member] | Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Interest rate swaps, assets	16,654	15,429
Direct Financing Leases and Other Assets [Member] | Fair Value, Inputs, Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Interest rate swaps, assets	0	0
Accrued Expenses [Member]
Assets and liabilities measured at fair value on a recurring basis
Contingent consideration	14,400
Accrued Expenses [Member] | Fair Value, Inputs, Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Contingent consideration	0
Accrued Expenses [Member] | Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Contingent consideration	0
Accrued Expenses [Member] | Fair Value, Inputs, Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Contingent consideration	14,400
Prepaid expenses and other current assets [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign currency forward contract	4,037
Prepaid expenses and other current assets [Member] | Fair Value, Inputs, Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign currency forward contract	0
Prepaid expenses and other current assets [Member] | Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign currency forward contract	4,037
Prepaid expenses and other current assets [Member] | Fair Value, Inputs, Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Foreign currency forward contract	0
Other non-current liabilities [Member]
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps, liabilities	213
Other non-current liabilities [Member] | Fair Value, Inputs, Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps, liabilities	0
Other non-current liabilities [Member] | Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps, liabilities	213
Other non-current liabilities [Member] | Fair Value, Inputs, Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Interest rate swaps, liabilities	0
Fair Value, Inputs, Level 1 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total assets at fair value	19,500	17,404
Total liabilities at fair value	0
Fair Value, Inputs, Level 1 [Member] | Cash and Cash Equivalents [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	4,720	2,348
Fair Value, Inputs, Level 1 [Member] | U.S. Equity Mutual Funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	9,022	8,409
Fair Value, Inputs, Level 1 [Member] | Foreign equity mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	2,623	5,188
Fair Value, Inputs, Level 1 [Member] | Fixed income mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	3,135	1,459
Fair Value, Inputs, Level 2 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total assets at fair value	20,691	15,429
Total liabilities at fair value	213
Fair Value, Inputs, Level 2 [Member] | Cash and Cash Equivalents [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 2 [Member] | U.S. Equity Mutual Funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 2 [Member] | Foreign equity mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 2 [Member] | Fixed income mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 3 [Member]
Assets and liabilities measured at fair value on a recurring basis
Total assets at fair value	0	0
Total liabilities at fair value	14,400
Fair Value, Inputs, Level 3 [Member] | Cash and Cash Equivalents [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 3 [Member] | U.S. Equity Mutual Funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 3 [Member] | Foreign equity mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Fair Value, Inputs, Level 3 [Member] | Fixed income mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	0	0
Cash and Cash Equivalents [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	4,720	2,348
U.S. Equity Mutual Funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	9,022	8,409
Foreign equity mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	2,623	5,188
Fixed income mutual funds [Member]
Assets and liabilities measured at fair value on a recurring basis
Investments held in Rabbi Trusts	$ 3,135	$ 1,459