Notes Payable (Details) (USD $)			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 2023 Notes	Apr. 30, 2013 2023 Notes	Mar. 31, 2014 Forward Contracts instrument	Dec. 31, 2013 Forward Contracts instrument	Apr. 30, 2013 Forward Contracts instrument
Debt Instrument [Line Items]
Original Principal				$ 350,000,000
Stated interest rate				3.30%
Proceeds from Issuance of Long-term Debt			347,406,000
Notes payable, unamortized discount	10,514,000	10,816,000		2,594,000
Effective Interest Rate				3.388%
Number of interest rate derivatives held					3	4	4
Derivative, Notional Amount					225,000,000	240,000,000	240,000,000
Interest rate cash flow hedge liability, fair value							3,156,000
Amount of cash flow hedge reported in AOCI							3,141,000
Proceeds from notes payable			344,266,000
Debt Issuance Cost			$ 3,140,000