Line of Credit (Details) (USD $)	6 Months Ended		1 Months Ended	6 Months Ended					6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2013 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member]	Jun. 30, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member]	Jul. 31, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member] Subsequent Event	Jun. 30, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member] Minimum [Member]	Jul. 31, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member] Minimum [Member] Subsequent Event	Jun. 30, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member] Maximum [Member]	Jun. 30, 2014 Unsecured Debt [Member] U.S. Bank and East-West Bank [Member] Revolving Credit Facility [Member] LIBOR [Member]
Line of Credit Facility [Line Items]
Increase in maximum borrowing capacity			$ 40,000,000
Maximum borrowing capacity			140,000,000	140,000,000.0	300,000,000.0
Basis spread on variable rate									2.75%
Rent adjusted fixed charge coverage ratio				3.73		1.50	1.50
Balance sheet leverage ratio				0.80			1.50	1.50
Covenant, tangible net worth				928,500,000		250,000,000	500,000,000.0
Line of credit facility covenant compliance minimum requirement of unrestricted cash and cash equivalents				610,700,000		40,000,000	40,000,000.0
Borrowings under line of credit	90,000,000	85,000,000		90,000,000
Maximum amount drawn on the unsecured credit facility at any one point				90,000,000
Remaining borrowing capacity				$ 140,000,000.0
Covenant, percent of new equity offerings					50.00%