Debt Revolving Credit Facility Narrative (Details) (USD $)	1 Months Ended		1 Months Ended			12 Months Ended
	Apr. 30, 2011 April 2011 Line of Credit [Member]	Aug. 31, 2011 April 2011 Line of Credit [Member]	Apr. 30, 2011 August 2006 Line of Credit [Member]	Oct. 31, 2012 April 2011 Line of Credit as Amended October 2012 [Member]	Apr. 30, 2011 April 2011 Line of Credit as Amended October 2012 [Member]	Dec. 31, 2013 April 2011 Line of Credit as Amended October 2012 [Member]
Line of Credit Facility [Line Items]
Debt Instrument, Basis Spread on Variable Rate	1.05%					0.975%
Line of Credit Facility, Commitment Fee Percentage	0.20%					0.15%
Issuance date of debt instrument	April 2011			October 2012
Line of credit facility term	5 years
Line of Credit Facility, Maximum Borrowing Capacity Before Increase	$ 300,000,000
Maximum borrowing capacity		450,000,000	250,000,000
Maturity date description			August 2011		April 2016
Remaining borrowing capacity						243,000,000
Amount to secure standby letters of credit						$ 2,000,000