Commitments and Contingencies (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Commitments and Contingencies [Line Items]
Rental expense for operating leases	$ 2,200,000	$ 2,000,000	$ 6,900,000	$ 5,300,000
Defined benefit plan employer matching contribution on first five percent of employee compensation			50.00%
Defined benefit plan employer contribution limit			6,000
Defined benefit plan employer contribution vesting period			5 years
Maximum [Member]
Commitments and Contingencies [Line Items]
Percentage of employees' eligible compensation for employer matching contribution			5.00%
Salaries And Related Expenses [Member]
Commitments and Contingencies [Line Items]
Defined benefit plan employer contribution	$ 200,000	$ 200,000	$ 700,000	$ 500,000