Leases (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Minimum Future Rental Receipts [Abstract]
2013	$ 335,434
2014	319,112
2015	276,155
2016	245,100
2017	222,542
Thereafter	1,111,022
Future Minimum Payments Receivable	2,509,365
Future Rental Payments [Abstract]
2013	2,572
2014	2,328
2015	2,300
2016	1,971
2017	1,924
Thereafter	15,885
Future Minimum Payments Due	26,980
Rent expense	1,198	776	955
Fixed rent per annum payment thereafter	1,153
Incentive from lessor	845
Office Space Leased for Regional Offices [Member]
Future Rental Payments [Abstract]
2013	82
2014	45
2015	36
2016	36
2017	9
Rent expense	$ 1,029	$ 1,392	$ 1,332

Fixed Rent Per Annum Payment Thereafter

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- Definition

This item represents the deferred credit for an incentive or inducement received by a lessee from a lessor, in order to motivate the lessee to enter the lease agreement, which incentive or inducement is to be recognized as a reduction of rental expense over the lease term.

+ References

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-Name Accounting Standards Codification

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-Glossary Lease Incentive

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-Name Statement of Financial Accounting Standard (FAS)

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- Definition

The total of future contractually required payments on leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within one year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the fifth year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the third year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due within the second year of the balance sheet date relating to leases defined as operating.

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For leases having an initial or remaining non-cancelable letter-terms in excess of one year, required rental payments due after the fifth year from the balance sheet date on leases defined as operating.

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Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

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Future rental payments receivable within one year of the balance sheet date under an operating lease.

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Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

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Future rental payments receivable within the third year from the balance sheet date under an operating lease.

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Future rental payments receivable within the second year from the balance sheet date under an operating lease.

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Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date.

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Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

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