Commitments and Contingencies (Details)					3 Months Ended		1 Months Ended	0 Months Ended	1 Months Ended	0 Months Ended						1 Months Ended	0 Months Ended			1 Months Ended	0 Months Ended
	Mar. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Mar. 31, 2015 Potential Claim for Pension Advisory Services [Member] USD ($)	Apr. 30, 2014 Potential Claim for Pension Advisory Services [Member] GBP (£)	Mar. 31, 2015 Commitments to fund certain limited partnerships or subsidiaries [Member] USD ($)	Dec. 31, 2014 Commitments to fund certain limited partnerships or subsidiaries [Member] USD ($)	Jan. 31, 2014 Northrop Grumman Corporation [Member] USD ($)	Sep. 14, 2010 Opry Mills Mall Limited Partnership [Member] USD ($)	Mar. 31, 2015 Opry Mills Mall Limited Partnership [Member] USD ($)	Mar. 31, 2015 Philips [Member] USD ($)	Jan. 02, 2014 Philips [Member] GBP (£)	Mar. 31, 2015 International Road Transport Union [Member] Litigation Award [Member] USD ($)	Jan. 26, 2015 International Road Transport Union [Member] Litigation Award [Member] CHF	Dec. 02, 2014 International Road Transport Union [Member] Litigation Award [Member] CHF	Jun. 01, 2007 International Road Transport Union [Member] Litigation Award [Member] CHF	Dec. 31, 2014 International Road Transport Union [Member] Litigation Award [Member] CHF	Jan. 26, 2015 International Road Transport Union [Member] Litigation USD Denominated Award [Member] USD ($)	Dec. 02, 2014 International Road Transport Union [Member] Litigation USD Denominated Award [Member] USD ($)	Jun. 01, 2007 International Road Transport Union [Member] Litigation USD Denominated Award [Member] USD ($)	Dec. 31, 2014 International Road Transport Union [Member] Litigation USD Denominated Award [Member] USD ($)	Jun. 01, 2007 International Road Transport Union [Member] Litigation Expenses and Interest [Member] USD ($)	Mar. 31, 2015 Versicherung Aktiengesellschaft [Member] Litigation Award [Member] USD ($)	Dec. 27, 2012 Versicherung Aktiengesellschaft [Member] Litigation Award [Member] EUR (€)
Legal, Guarantees and Indemnifications
Range of possible loss, minimum	$ 0
Range of possible loss, maximum	600,000,000
Damages sought							340,000,000	200,000,000		281,000,000	189,000,000	48,000,000			46,000,000				3,000,000		30,000,000	199,000,000	183,000,000
Amount of coverage for damages contended by the insurers								50,000,000
Difference amount of damages sought by the client								150,000,000
Damages awarded excluding interest and costs												17,000,000		16,800,000				3,100,000
Damages awarded									200,000,000			29,000,000				27,900,000				5,000,000
Case settlement amount												13,000,000	12,800,000				4,700,000
Settlement, maximum liability												9,000,000	8,700,000				115,000
Estimate of possible loss			67,000,000	45,000,000
Maximum potential funding under commitments	77,000,000	112,000,000			12,000,000	14,000,000
Letters of credit outstanding	68,000,000	95,000,000
Commitments funded					$ 2,000,000