Income Taxes (Deferred Income Tax Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Income Taxes
Deferred tax liability - depreciation and amortization	$ (3,017)
Allowance for uncollectible receivables	5,744	5,845
Deferred revenue	2,464	982
Accrued compensation	5,677	4,822
Accrued office consolidation costs	383	371
Interest rate derivatives	208	197
Deferred tax asset - depreciation and amortization		804
Share-based compensation	5,468	4,447
Forgivable loans	3,692	3,553
Tax credits and capital loss carry forward	603	1,835
Other	305	140
Deferred tax assets	24,544	22,996
Acquisition costs - domestic acquisitions	(67,654)	(56,037)
Acquisition costs - foreign acquistions	(2,147)	(2,565)
Deferred tax liabilities, prepaid expenses	(1,528)	(1,129)
Deferred tax liabilities	(74,346)	(59,731)
Net deferred tax liabilities	$ (49,802)	$ (36,735)