Capital and Financing Transactions - Notes Payable (Details) (USD $)		6 Months Ended			6 Months Ended			6 Months Ended		0 Months Ended		0 Months Ended												0 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Working Capital Revolving Credit Facility	Jun. 30, 2014 Unsecured Revolving Credit Facility	Apr. 02, 2014 Unsecured Revolving Credit Facility	Jun. 30, 2014 Unsecured Term Loan $125 million		Apr. 02, 2014 Unsecured Term Loan $125 million	Jun. 30, 2014 Unsecured Term Loan $120 million	Apr. 02, 2014 Unsecured Term Loan $120 million	Apr. 02, 2014 Line of Credit Revolving Credit Facility	Jun. 30, 2014 Line of Credit Revolving Credit Facility	Apr. 02, 2014 Line of Credit LIBOR Revolving Credit Facility	Apr. 02, 2014 Line of Credit Minimum LIBOR Revolving Credit Facility	Apr. 02, 2014 Line of Credit Maximum LIBOR Revolving Credit Facility	Apr. 02, 2014 Seven-year Term Loan Unsecured Debt Draw	Apr. 02, 2014 Seven-year Term Loan Unsecured Debt LIBOR	Apr. 02, 2014 Seven-year Term Loan Unsecured Debt Minimum LIBOR	Apr. 02, 2014 Seven-year Term Loan Unsecured Debt Maximum LIBOR	Apr. 02, 2014 Five-year Term Loan Unsecured Debt	Apr. 02, 2014 Five-year Term Loan Unsecured Debt LIBOR	Apr. 02, 2014 Five-year Term Loan Unsecured Debt Minimum LIBOR	Apr. 02, 2014 Five-year Term Loan Unsecured Debt Maximum LIBOR	Apr. 02, 2014 Amended Working Capital Revolving Credit Facility Revolving Credit Facility	Apr. 08, 2014 First Mortgage Bank of America Center	Apr. 02, 2014 First Mortgage Bank of America Center
Debt Instrument [Line Items]
Interest Rate	2.91%	1.60%	1.60%		2.51%	[1]		4.31%
Maturity		Mar. 30, 2018	Mar. 30, 2018		Mar. 29, 2019	[1]		Mar. 31, 2021
Outstanding Balance	$ 377,000,000	$ 0	$ 27,000,000		$ 250,000,000	[1]		$ 100,000,000
Maximum borrowing capacity										250,000,000.0					100,000,000.0				250,000,000.0				10,000,000.0
Term of debt instrument															7 years				5 years
Debt instrument face amount				215,000,000			125,000,000		120,000,000
Term of debt extension option										1 year
Variable reference rate on debt												LIBOR				LIBOR				LIBOR
Basis spread on variable rate (in percent)													1.40%	2.00%			1.75%	2.30%			1.35%	1.90%
Interest rate during period on debt (in percent)												1.40%				1.75%				1.35%
Interest rate at period end (in percent)											1.60%				4.31%				2.51%
Number of draws allowed over 12-month period															2
Repayment of the first mortgage debt																									33,900,000
Loss on extinguishment of debt																								$ 339,000

[1] Represents a weighted average interest rate.