CONSOLIDATED STATEMENTS OF INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues:
Investment management fees	$ 549,231	$ 530,599	$ 457,538
Underwriting and distribution fees	496,465	469,484	410,380
Shareholder service fees	128,109	122,449	110,348
Total	1,173,805	1,122,532	978,266
Operating expenses:
Underwriting and distribution	589,981	560,219	493,456
Compensation and related costs (including share-based compensation of $48,748, $45,384 and $39,128, respectively)	171,775	157,332	138,207
General and administrative	75,332	74,110	60,785
Subadvisory fees	21,009	29,885	27,823
Depreciation	13,211	14,764	13,525
Total	871,308	836,310	733,796
Operating income	302,497	286,222	244,470
Investment and other income	9,817	2,105	8,619
Interest expense	(11,311)	(11,408)	(12,728)
Income from continuing operations before provision for income taxes	301,003	276,919	240,361
Provision for income taxes	108,475	104,714	86,933
Income from continuing operations	192,528	172,205	153,428
Income (loss) from discontinued operations net of tax expense of $1,058, $2,556 and $2,592, respectively	(41,576)	3,254	3,531
Net income	$ 150,952	$ 175,459	$ 156,959
Net income per share, basic and diluted:
Income from continuing operations (in dollars per share)	$ 2.25	$ 2.01	$ 1.79
Income (loss) from discontinued operations (in dollars per share)	$ (0.49)	$ 0.04	$ 0.04
Net income (in dollars per share)	$ 1.76	$ 2.05	$ 1.83
Weighted average shares outstanding:
Basic (in shares)	85,726	85,783	85,618
Diluted (in shares)	85,728	85,793	85,647