Benefit Plans (Details 4) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012 item	Dec. 31, 2011 item
Multiemployer plans
Number of employees employed by the entity	24,000	25,000	12,000
Expenses for contributions not reimbursed by clients and related to multiemployer defined benefit and defined contribution plans	$ 621	$ 762	$ 710
Red Zone | Maximum
Multiemployer plans
Multiemployer plans funded status (as a percent)	65.00%
Yellow Zone | Maximum
Multiemployer plans
Multiemployer plans funded status (as a percent)	80.00%
Green Zone | Minimum
Multiemployer plans
Multiemployer plans funded status (as a percent)	80.00%
Teamsters Local Union 727 | Minimum
Multiemployer plans
Entity's contributions as a percentage of total contributions	5.00%
Multiemployer defined benefit pension plans | Teamsters Local Union 727 | Green Zone
Multiemployer plans
Contributions	$ 3,376	$ 3,617	$ 2,500