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Debt (Details 4) |  |  |  |  |  |  |  | 1 Months Ended | 12 Months Ended
--- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Dec. 28, 2016 USD ($) | Dec. 17, 2015 USD ($) | Aug. 28, 2015 USD ($) | Jun. 29, 2015 USD ($) | May 06, 2015 USD ($) extension | May 14, 2014 USD ($) | Feb. 14, 2012 USD ($) | Dec. 31, 2014 USD ($) | Dec. 31, 2016 USD ($) | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
(Loss) gain on early extinguishment of debt |  |  |  |  |  |  |  |  | $ 1,110,000 | $ (85,275,000) | $ 9,552,000
Term Credit Facility Effective February 2012 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Initial amount borrowed |  |  |  |  |  |  | $ 250,000,000 |  |  |  |
Term Credit Facility Effective August 2012 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  | 120,000,000 |  |
Term Credit Facility Effective September 2011 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Repayments of debt |  |  |  |  |  |  |  |  |  | 150,000,000 | $ 100,000,000
Fixed rate mortgage loans [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Debt settled through the surrender of real estate assets |  |  | $ 150,000,000 |  |  |  |  |  |  |  |
Minimum [Member] | Term Credit Facility Effective February 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  |  |  |  | 0.90% |  |  |  |  |  |
Maximum [Member] | Term Credit Facility Effective February 2012 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  |  |  |  | 1.85% |  |  |  |  |  |
Secured Loans Due November 2015 And January 2016 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
(Loss) gain on early extinguishment of debt |  |  |  |  |  |  |  | $ 9,100,000 |  |  |
Secured Loan Due November 2015 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate (as a percent) |  |  |  |  |  |  |  | 5.53% |  |  | 5.53%
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement |  |  |  |  |  |  |  | $ 103,000,000 |  |  |
Secured Loan Due January 2016 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate (as a percent) |  |  |  |  |  |  |  | 5.56% |  |  | 5.56%
Amount of loans repaid upon entry into Revolving Credit Facility and Term Loan Agreement |  |  |  |  |  |  |  | $ 108,500,000 |  |  |
Revolving Credit Facility [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Maximum availability |  |  |  |  |  |  |  |  | 800,000,000 |  |
Expansion right, maximum borrowing capacity |  |  |  |  |  |  |  |  | $ 1,300,000,000 |  |
Amount available as a percentage of unencumbered Asset value |  |  |  |  |  |  |  |  | 60.00% |  |
Line of credit facility, extension fee percentage |  |  |  |  |  |  |  |  | 0.075% |  |
Weighted average borrowings |  |  |  |  |  |  |  |  | $ 90,300,000 | $ 125,000,000 |
Weighted average interest rate (as a percent) |  |  |  |  |  |  |  |  | 1.64% | 1.40% |
Line of Credit [Member] | Term Credit Facility Effective February 2012 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Maximum availability |  |  |  |  | $ 300,000,000 |  |  |  |  |  |
Increase to maximum borrowing capacity |  |  |  |  | 200,000,000 |  |  |  |  |  |
Aggregate maximum borrowing capacity |  |  |  |  | $ 500,000,000 |  |  |  |  |  |
Line of Credit [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Number of extensions | extension |  |  |  |  | 2 |  |  |  |  |  |
Extension option period (in years) |  |  |  |  | 6 months |  |  |  |  |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Minimum [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commitment fee percentage |  |  |  |  | 0.125% |  |  |  |  |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  |  |  |  | 0.875% |  |  |  |  |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Commitment fee percentage |  |  |  |  | 0.30% |  |  |  |  |  |
Line of Credit [Member] | Revolving Credit Facility [Member] | Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  |  |  |  | 1.60% |  |  |  |  |  |
Unsecured Debt [Member] | Term Credit Facility Effective December 2015 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Maximum availability |  | $ 250,000,000 |  |  |  |  |  |  |  |  |
Remaining borrowing capacity |  |  |  |  |  |  |  |  | $ 150,000,000 |  |
Initial amount borrowed |  | $ 100,000,000 |  |  |  |  |  |  |  |  |
Unsecured Debt [Member] | Term Credit Facility Effective December 2016 [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Initial amount borrowed | $ 150,000,000 |  |  |  |  |  |  |  |  |  |
Unsecured Debt [Member] | Minimum [Member] | Term Credit Facility Effective December 2015 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  | 1.40% |  |  |  |  |  |  |  |  |
Unsecured Debt [Member] | Maximum [Member] | Term Credit Facility Effective December 2015 [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Variable rate, spread (as a percent) |  | 2.35% |  |  |  |  |  |  |  |  |
Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Redemption price (percent) |  |  |  |  |  |  |  |  | 100.00% |  |
Senior Notes [Member] | 5.0% Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Loan amount |  |  |  | $ 300,000,000 |  |  |  |  |  |  |
Stated interest rate (as a percent) |  |  |  | 5.00% |  |  |  |  | 5.00% |  |
Debt issuance as a percentage of principal amount |  |  |  | 99.51% |  |  |  |  |  |  |
Unamortized discount included in carrying value |  |  |  |  |  |  |  |  | $ 3,000,000 | $ 3,300,000 |
Interest rate on debt (as a percent) |  |  |  |  |  |  |  |  | 5.15% |  |
Proceeds from debt, net |  |  |  | $ 296,600,000 |  |  |  |  |  |  |
Senior Notes [Member] | 5.0% Senior Notes [Member] | Adjusted Treasury [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis points used in determining redemption price prior to maturity |  |  |  |  |  |  |  |  | 0.45% |  |
Senior Notes [Member] | 3.70% Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Initial amount borrowed |  |  |  |  |  | $ 297,300,000 |  |  |  |  |
Loan amount |  |  |  |  |  |  |  |  | $ 300,000,000 |  |
Stated interest rate (as a percent) |  |  |  |  |  | 3.70% |  |  | 3.70% |  |
Debt issuance as a percentage of principal amount |  |  |  |  |  | 99.739% |  |  |  |  |
Unamortized discount included in carrying value |  |  |  |  |  |  |  |  | $ 1,700,000 | 2,100,000 |
Interest rate on debt (as a percent) |  |  |  |  |  |  |  |  | 3.85% |  |
Senior Notes [Member] | 3.70% Senior Notes [Member] | Adjusted Treasury [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis points used in determining redemption price prior to maturity |  |  |  |  |  |  |  |  | 0.25% |  |
Senior Notes [Member] | 3.60% Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate (as a percent) |  |  |  |  |  |  |  |  | 3.60% |  |
Unamortized discount included in carrying value |  |  |  |  |  |  |  |  | $ 2,000,000 | 2,200,000 |
Interest rate on debt (as a percent) |  |  |  |  |  |  |  |  | 3.70% |  |
Senior Notes [Member] | 3.60% Senior Notes [Member] | Adjusted Treasury [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis points used in determining redemption price prior to maturity |  |  |  |  |  |  |  |  | 0.30% |  |
Senior Notes [Member] | 5.250% Senior Notes [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Stated interest rate (as a percent) |  |  |  |  |  |  |  |  | 5.25% |  |
Unamortized discount included in carrying value |  |  |  |  |  |  |  |  | $ 3,400,000 | $ 3,800,000 |
Interest rate on debt (as a percent) |  |  |  |  |  |  |  |  | 5.49% |  |
Senior Notes [Member] | 5.250% Senior Notes [Member] | Adjusted Treasury [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
Basis points used in determining redemption price prior to maturity |  |  |  |  |  |  |  |  | 0.40% |  |
Operating properties, net [Member] | 15000 and 15010 Conference Center Drive [Member] |  |  |  |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |  |  |  |
(Loss) gain on early extinguishment of debt |  |  | (84,800,000) |  |  |  |  |  |  |  |
Debt settled through the surrender of real estate assets |  |  | $ 150,000,000 |  |  |  |  |  |  |  |

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