Organization and Summary of Significant Accounting Policies (Details Textual) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012 Practice_Groups	Dec. 31, 2011	Dec. 31, 2010
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Intangible assets amortization period	8 years 4 months 24 days
Organization and Summary of Significant Accounting Policies (Additional Textual) [Abstract]
Number of practice groups	4
Contract payment terms	90 days
Total personnel costs	$ 507.7	$ 476.0	$ 481.7
Total occupancy costs	45.0	44.4	45.5
Administrative service agreements [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Fees earned under administrative service agreement	$ 116.1	$ 109.1	$ 110.1
Stock options [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Option vesting term	4 years
Maximum [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Intangible assets amortization period	15 years
Minimum [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Intangible assets amortization period	2 years
Software [Member] | Maximum [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Intangible assets amortization period	7 years
Software purchased or developed, estimated useful life	7 years
Software [Member] | Minimum [Member]
Organization and Summary of Significant Accounting Policies (Textual) [Abstract]
Software purchased or developed, estimated useful life	2 years