Segment Information Revenue from External Customers by Products and Services (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Jan. 31, 2016	[1]	Oct. 31, 2015	Jul. 31, 2015	[2]	Apr. 30, 2015	Jan. 31, 2015	Oct. 31, 2014	[3]	Jul. 31, 2014	Apr. 30, 2014	Jan. 31, 2016	Jan. 31, 2015	Jan. 31, 2014
Revenue from External Customer [Line Items]
Net sales	$ 1,213.6		$ 938.2	$ 990.5		$ 962.4	$ 1,285.3	$ 959.6		$ 992.9	$ 1,012.1	$ 4,104.9	$ 4,249.9	$ 4,031.1
Statement, fine and solitare jewelry [Member]
Revenue from External Customer [Line Items]
Net sales												910.8	930.2	916.8
Engagement jewelry and wedding bands [Member]
Revenue from External Customer [Line Items]
Net sales												1,170.2	1,245.1	1,182.2
Fashion jewelry [Member]
Revenue from External Customer [Line Items]
Net sales												1,716.1	1,755.2	1,618.2
Other products/services [Member]
Revenue from External Customer [Line Items]
Net sales												$ 307.8	$ 319.4	$ 313.9

[1] On a pre-tax basis, includes charges for the quarter ended January 31, 2016 of: i.$28.3 million, which reduced net earnings per diluted share by $0.14, associated with an impairment charge related to a financing arrangement with Koidu Limited (see "Note B - Summary of Significant Accounting Policies" and "Note J - Commitments and Contingencies"); andii.$8.8 million, which reduced net earnings per diluted share by $0.04, associated with severance related to staffing reductions and subleasing of certain office space for which only a portion of the Company's future rent obligations will be recovered (see "Note J - Commitments and Contingencies").

[2] On a pre-tax basis, includes a charge of $9.6 million for the quarter ended July 31, 2015, which reduced net earnings per diluted share by $0.05, associated with an impairment charge related to a financing arrangement with Koidu Limited (see "Note B - Summary of Significant Accounting Policies" and "Note J - Commitments and Contingencies").

[3] On a pre-tax basis, includes a charge of $93.8 million for the quarter ended October 31, which reduced net earnings per diluted share by $0.47, associated with the redemption of $400.0 million in aggregate principal amount of the Private Placement Notes prior to their scheduled maturities (see "Note G - Debt").