Employee Retirement Plans (Details) - Savings and Investment Plan - USD ($)	1 Months Ended	12 Months Ended
	Jan. 31, 2015	Jan. 31, 2017	Jan. 31, 2016	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Employer matching percentage of employee contributions on first level of eligible compensation (as a percent)		100.00%
Percentage of eligible compensation, first level, matched by employer (as a percent)		3.00%
Employer match of employee contributions on the second level of eligible compensation (as a percent)		$ 50
Percentage of eligible compensation, second level, partially matched by employer (as a percent)		2.00%
Total expense for plans established pursuant to Section 401(k)	$ 400,000	$ 3,400,000	$ 3,600,000	$ 2,800,000
Compensation expense		$ 2,500,000	$ 2,400,000	$ 100,000
Maximum
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution savings and investment plan, employees contribution rate		100.00%