Consolidated Statement of Shareholders' Equity Consolidated Statement of Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Common Stock, Shares, Issued at Jan. 31, 2018	59,246,000
Stockholders' Equity Balance at Jan. 31, 2018	$ 2,921,492	$ 89	$ 827,301	$ (940,124)	$ 2,745,934	$ 288,292
Issuance of treasury stock for benefit plan and equity-based awards exercised	(5,814)	0	(12,771)	6,957	0	0
Stock-based compensation expense	7,587	0	7,587	0	0	0
Other comprehensive income (loss)	(88,252)	0	0	0	0	(88,252)
Net income	$ 33,699	0	0	0	33,699	0
Common Stock, Shares, Issued at Apr. 30, 2018	59,246,000
Stockholders' Equity Balance at Apr. 30, 2018	$ 2,868,712	89	822,117	(933,167)	2,779,633	200,040
Common Stock, Shares, Issued at Jan. 31, 2018	59,246,000
Stockholders' Equity Balance at Jan. 31, 2018	$ 2,921,492	89	827,301	(940,124)	2,745,934	288,292
Other comprehensive income (loss)	(281,737)
Net income	$ 223,781
Common Stock, Shares, Issued at Oct. 31, 2018	59,246,000
Stockholders' Equity Balance at Oct. 31, 2018	$ 2,837,789	89	836,520	(975,090)	2,969,715	6,555
Common Stock, Shares, Issued at Apr. 30, 2018	59,246,000
Stockholders' Equity Balance at Apr. 30, 2018	$ 2,868,712	89	822,117	(933,167)	2,779,633	200,040
Issuance of treasury stock for benefit plan and equity-based awards exercised	220	0	(1,083)	1,303	0	0
Stock-based compensation expense	7,968	0	7,968	0	0	0
Other comprehensive income (loss)	(102,055)	0	0	0	0	(102,055)
Net income	$ 75,866	0	0	0	75,866	0
Common Stock, Shares, Issued at Jul. 31, 2018	59,246,000
Stockholders' Equity Balance at Jul. 31, 2018	$ 2,850,711	89	829,002	(931,864)	2,855,499	97,985
Repurchases of common stock	(43,798)	0	0	(43,798)	0	0
Issuance of treasury stock for benefit plan and equity-based awards exercised	(49)	0	(621)	572	0	0
Stock-based compensation expense	8,139	0	8,139	0	0	0
Other comprehensive income (loss)	(91,430)	0	0	0	0	(91,430)
Net income	$ 114,216	0	0	0	114,216	0
Common Stock, Shares, Issued at Oct. 31, 2018	59,246,000
Stockholders' Equity Balance at Oct. 31, 2018	$ 2,837,789	89	836,520	(975,090)	2,969,715	6,555
Common Stock, Shares, Issued at Jan. 31, 2019	59,246,000
Stockholders' Equity Balance at Jan. 31, 2019	$ 2,936,723	89	844,206	(1,037,872)	3,086,514	43,786
Repurchases of common stock	(35,681)	0	0	(35,681)	0	0
Issuance of treasury stock for benefit plan and equity-based awards exercised	(8,107)	0	(16,003)	7,896	0	0
Stock-based compensation expense	8,305	0	8,305	0	0	0
Other comprehensive income (loss)	(40,734)	0	0	0	0	(40,734)
Net income	$ 55,400	0	0	0	55,400	0
Common Stock, Shares, Issued at Apr. 30, 2019	59,246,000
Stockholders' Equity Balance at Apr. 30, 2019	$ 2,915,906	89	836,508	(1,065,657)	3,141,914	3,052
Common Stock, Shares, Issued at Jan. 31, 2019	59,246,000
Stockholders' Equity Balance at Jan. 31, 2019	$ 2,936,723	89	844,206	(1,037,872)	3,086,514	43,786
Other comprehensive income (loss)	(39,012)
Net income	$ 225,420
Common Stock, Shares, Issued at Oct. 31, 2019	59,246,000
Stockholders' Equity Balance at Oct. 31, 2019	$ 2,968,285	89	846,636	(1,195,148)	3,311,934	4,774
Common Stock, Shares, Issued at Apr. 30, 2019	59,246,000
Stockholders' Equity Balance at Apr. 30, 2019	$ 2,915,906	89	836,508	(1,065,657)	3,141,914	3,052
Repurchases of common stock	(82,011)	0	0	(82,011)	0	0
Issuance of treasury stock for benefit plan and equity-based awards exercised	(25)	0	(1,404)	1,379	0	0
Stock-based compensation expense	8,055	0	8,055	0	0	0
Other comprehensive income (loss)	(31,553)	0	0	0	0	(31,553)
Net income	$ 79,250	0	0	0	79,250	0
Common Stock, Shares, Issued at Jul. 31, 2019	59,246,000
Stockholders' Equity Balance at Jul. 31, 2019	$ 2,889,622	89	843,159	(1,146,289)	3,221,164	(28,501)
Repurchases of common stock	(49,300)	0	0	(49,300)	0	0
Issuance of treasury stock for benefit plan and equity-based awards exercised	245	0	(196)	441	0	0
Stock-based compensation expense	7,347	0	7,347	0	0	0
Adjustments to Additional Paid in Capital, Other	(3,674)	0	(3,674)	0	0	0
Other comprehensive income (loss)	33,275	0	0	0	0	33,275
Net income	$ 90,770	0	0	0	90,770	0
Common Stock, Shares, Issued at Oct. 31, 2019	59,246,000
Stockholders' Equity Balance at Oct. 31, 2019	$ 2,968,285	$ 89	$ 846,636	$ (1,195,148)	$ 3,311,934	$ 4,774