Credit Facility (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Feb. 28, 2015	Mar. 31, 2015
Credit facility
Amount outstanding		$ 0
Remaining borrowing capacity		35.0
Revolving line of credit
Credit facility
Maximum borrowing capacity	35.0
Increase in maximum borrowing capacity, subject to lender's consent	15.0
Maximum borrowing capacity, subject to lender's consent	50
Quick ratio minimum	1.5
Maximum consolidated leverage ratio, upper end of range	3.00
Maximum consolidated leverage ratio, lower end of range	2.50
Minimum fixed charge coverage ratio	1.25
Revolving line of credit | Minimum
Credit facility
Unused facility fee (as a percent)	0.00%
Revolving line of credit | Maximum
Credit facility
Unused facility fee (as a percent)	0.20%
Revolving line of credit | Prime rate | Minimum
Credit facility
Variable rate basis spread (as a percent)	(0.25%)
Revolving line of credit | Prime rate | Maximum
Credit facility
Variable rate basis spread (as a percent)	0.50%
Revolving line of credit | LIBOR | Minimum
Credit facility
Variable rate basis spread (as a percent)	1.75%
Revolving line of credit | LIBOR | Maximum
Credit facility
Variable rate basis spread (as a percent)	2.50%
Letters of credit
Credit facility
Maximum borrowing capacity	$ 10.0