Leases (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended				6 Months Ended
	Nov. 27, 2012 BMO Harris Equipment Finance Company [Member]	Nov. 27, 2012 Capital Source Bank [Member]	Dec. 27, 2012 BB&T Equipment Finance [Member]	Feb. 22, 2012 Wells Fargo Bank Northwest [Member]	Jun. 30, 2013 U.S. Flag PCTC [Member]	Jun. 30, 2013 International Flag PCTC [Member]
Capital Leased Assets [Line Items]
Lease expiration date					Oct. 31, 2015	May 31, 2019
Book value of leased asset						$ 16.2
Operating Leased Assets [Line Items]
Transaction generated gross proceeds	32.0	31.0	32.0	59.0
Repayment of debt from proceeds of sale and leaseback transaction				54.5
Lease term	7 years	6 years	6 years	10 years
Gain on this sale-leaseback	$ 8.0	$ 11.7		$ 14.9