Basis of Presentation Schedule of Error Corrections and Prior Period Adjustment - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Gross profit	$ 98,318	$ 95,917		$ 175,816		$ 173,680
Income from operations	35,009	32,133		51,286		51,738
Net income	$ 21,509	$ 20,451		$ 31,560	$ 30,993	$ 32,538
Restatement Adjustment
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Gross profit			$ 2,300
Income from operations			2,000
Net income			$ 1,300