Credit Facility (Details)		3 Months Ended
	Feb. 02, 2016 USD ($)	Mar. 31, 2016 USD ($)	Mar. 31, 2015 USD ($)	Dec. 31, 2011 USD ($)
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 100,000,000
Debt covenant, maximum debt to total capitalization ratio	0.35
Outstanding balance on credit facility		$ 0	$ 0
Interest expense incurred		$ 0	$ 0
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 50,000,000
Credit agreement term	4 years
Current borrowing capacity				$ 100,000,000
Letter of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 20,000,000			20,000,000
Swing Line of Credit [Member]
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 5,000,000			$ 5,000,000