Employee Benefit Plans - Multi-Employer Plan (Details) (USD $)	3 Months Ended			6 Months Ended	9 Months Ended	12 Months Ended					12 Months Ended
	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Dec. 31, 2011	Mar. 31, 2012	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011 Western Conference of Teamsters Pension Plan	Oct. 31, 2011 Western Conference of Teamsters Pension Plan	Jun. 30, 2013 Program for Enhanced Early Retirement	Jun. 30, 2013 Multiemployer Plans, Pension Western Conference of Teamsters Pension Plan		Jun. 30, 2012 Multiemployer Plans, Pension Western Conference of Teamsters Pension Plan		Jun. 30, 2011 Multiemployer Plans, Pension Western Conference of Teamsters Pension Plan		Jun. 30, 2013 Multiemployer Plans, Pension All Other Plans		Jun. 30, 2012 Multiemployer Plans, Pension All Other Plans		Jun. 30, 2011 Multiemployer Plans, Pension All Other Plans		Jun. 30, 2013 Other Postretirement Benefit Plans, Defined Contribution [Member]	Jun. 30, 2012 Other Postretirement Benefit Plans, Defined Contribution [Member]	Jun. 30, 2011 Other Postretirement Benefit Plans, Defined Contribution [Member]
Multiemployer Plans
Multiemployer Plan, Period Contributions																								$ 5,800,000	$ 5,800,000	$ 5,400,000
Employer contributions												3,064,000	[1],[2],[3]	3,048,000	[1],[2],[3]	2,929,000	[1],[2],[3]	37,000	[4]	113,000	[4]	254,000	[4]
Withdrawal obligation										0
Employer contributions (percentage)									5.00%		6.50%
Employer contributions (hours)											T173H
Pension withdrawal expense	$ 220,000	$ 0	$ 4,348,000	$ 4,348,000	$ 4,348,000	$ 0	$ 4,568,000	$ 0

[1] Individually significant plan.

[2] Less than 5% of total contribution to WCTPP based on WCTPP's most recent annual report on Form 5500 for the calendar year ended December 31, 2012.

[3] The Company guarantees that one hundred seventy-three (173) hours will be contributed upon for all employees who are compensated for all available straight time hours for each calendar month. An additional 6.5% of the basic contribution must be paid for PEER or the Program for Enhanced Early Retirement.

[4] Includes plans that are not individually significant.