Accounting for Income Taxes - Additional Information (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2013	Mar. 31, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Income Taxes [Line Items]
Provision for income taxes	$ 8,246,000		$ 8,061,000	$ 11,166,000	$ 14,271,000
Income tax expense (benefit) related to googdwill and long-lived assets				5,800,000
Income tax expense				9,700,000
Income Tax Expense (Benefit), Deductible, Impairment Losses, Amount				4,000,000
Effective Income Tax Rate, Continuing Operations	22.00%		22.10%	(745.90%)	22.40%
Tax credit		500,000
Valuation allowance, deferred tax asset	30,300,000			30,300,000
Increase in gross unrecognized tax benefits	1,900,000
Unrecognized tax benefits	$ 24,000,000			$ 24,000,000