Employee Benefit Plans Multiemployer Defined Benefit Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Jun. 30, 2011	Dec. 31, 2010	Jun. 30, 2010	Jun. 30, 2012
Multiemployer Plans [Abstract]
Eligible age for multiemployer defined benefit plan (in years)	21
Multiemployer defined benefit plan requisite service period (in years)	1
Multiemployer defined benefit plan contributions by employer	$ 595,000	$ 605,000
Multiemployer defined benefit plan contribution percentage	5.00%
Multiemployer defined benefit plan expense	602,000	302,000		115,000
Multiemployer defined benefit plan funding target			80.90%			83.20%
Multiemployer defined benefit plan contributions by plan participants			$ 299,700,000		$ 203,600,000