Derivative Instruments and Hedging Activities (Details) (USD $)
 3 Months Ended 6 Months Ended 3 Months Ended 6 Months Ended 6 Months Ended 6 Months Ended 6 Months Ended 6 Months Ended
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Jun. 30, 2012
Jun. 30, 2013
Interest rate swaps
Cash flow hedging
Jun. 30, 2012
Interest rate swaps
Cash flow hedging
Jun. 30, 2013
Interest rate swaps
Cash flow hedging
Jun. 30, 2012
Interest rate swaps
Cash flow hedging
Jun. 30, 2013
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Dec. 31, 2012
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Jun. 30, 2013
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 5.8% maturing 03-01-2016
Dec. 31, 2012
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 5.8% maturing 03-01-2016
Jun. 30, 2013
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 4.9% maturing 11-30-2013
Dec. 31, 2012
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 4.9% maturing 11-30-2013
Jun. 30, 2013
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 3.5% maturing 09-26-2014
Dec. 31, 2012
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 3.5% maturing 09-26-2014
Jun. 30, 2013
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 3.2% maturing 09-04-2015
Dec. 31, 2012
Interest rate swaps
Derivative liabilities, deferred rent and other liabilities
Interest rate swap, 3.2% maturing 09-04-2015
Derivatives, Fair Value [Line Items]                                    
Outstanding notional amount                     $ 6,895,000   $ 111,111,000   $ 38,250,000   $ 32,400,000  
Interest rate                     5.80%   4.90%   3.50%   3.20%  
Effective date                     Feb. 20, 2009   Feb. 28, 2011   Sep. 26, 2011   Sep. 05, 2012  
Maturity date                     Mar. 01, 2016   Nov. 30, 2013   Sep. 26, 2014   Sep. 05, 2015  
Fair value of liability                 (1,246,000) (2,181,000) (362,000) (481,000) (529,000) (1,133,000) (221,000) (321,000) (134,000) (246,000)
Amount of gain (loss) recognized in other comprehensive income         214,000 573,000 641,000 788,000                    
Amount of loss reclassified from accumulated other comprehensive income to earnings (823,000) 0 (823,000) 0 823,000 [1] 0 [1] 823,000 [1] 0 [1]                    
Amount of gain recognized in earnings         294,000 0 294,000 0                    
Unrealized loss on derivatives     $ 641,000 $ 788,000                 $ 529,000          
[1] In connection with the Merger, the Company terminated the interest rate swap agreement associated with $111.1 million of variable rate debt. As a result, the Company recorded an unrealized loss of $529,000 in merger related expenses, $823,000 of which was previously recorded in accumulated other comprehensive income. The remaining interest rate swaps were considered effective during the three and six months ended June 30, 2013. In addition, there were no portions of the change in the fair value of the interest rate swap agreements that were considered ineffective during the three and six months ended June 30, 2012.