Quarterly Information (Information) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Quarterly Financial Information Disclosure [Abstract]
Revenue Steam Products and Services	$ 363,294	$ 340,520	$ 365,240	$ 372,855	$ 406,422	$ 344,086	$ 330,358	$ 314,371
Interest Expense	6,416	6,306	6,383	6,242	4,823	3,698	2,349	2,341	25,347		13,211		12,234
Results of Operations, Income before Income Taxes	45,026	39,023	3,875	50,684	66,817	(142,556)	35,945	39,565
Net income/(loss)	27,016	22,304	3,416	31,398	41,394	(84,336)	21,109	23,740
Earnings Per Share Basic									$ 1.61	[1]	$ 0.04	[1]	$ 1.79	[1]
Earnings Per Share Diluted									$ 1.33		$ 0.03		$ 1.56
Total non-interest expenses	311,852	295,191	354,982	315,929	334,782	482,944	292,064	272,465	1,277,954		1,382,255		970,222
Net revenues	$ 356,878	$ 334,214	$ 358,857	$ 366,613	$ 401,599	$ 340,388	$ 328,009	$ 312,030	$ 1,416,562		$ 1,382,026		$ 1,090,636

[1] Diluted earnings per share is computed on the basis of the weighted average number of shares of common stock plus the effect of dilutive potential common shares outstanding during the period using the treasury stock method. Diluted earnings per share include stock options and units.