Stock Based Compensation and Other Benefit Plans (Details Textual)	1 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2014 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	May 31, 2017 shares	May 31, 2016 shares	May 31, 2015 shares
Options granted | shares			0
Dividend yield			0.00%
Value of options exercised			$ 1,100,000	$ 100,000	$ 300,000
Proceeds from options exercised			2,600,000	700,000	600,000
Tax benefit from compensation expense			1,700,000	2,300,000	2,600,000
Tax benefits from exercise of stock options			$ 300,000	100,000	100,000
Maximum annual contributions per employee (percent)			50.00%
Employer discretionary contribution amount			$ 1,400,000	$ 900,000	$ 3,200,000
Restricted stock [Member]
Estimated fair value at date of grant (in dollars per share) | $ / shares			$ 7.80
Employee Stock Option [Member]
Vesting period			3 years
Expiration period			10 years
Dividend yield				0.00%	0.00%
Stock Appreciation Rights (SARs) [Member]
Cash settlement of stock appreciation rights (in dollars per share) | $ / shares			$ 7.89
Cash settled stock appreciation rights fair value (in dollars per share) | $ / shares			$ 1.58
Share-based arrangement, liability			$ 100,000
Performance Based Restricted Stock Units [Member]
Estimated fair value at date of grant (in dollars per share) | $ / shares			$ 0.00	$ 5.18	$ 10.06
Vesting period		3 years
Dividend yield				0.00%	0.00%
Allocated share-based compensation expense		$ 1,300,000	$ 1,000,000	$ 1,000,000	$ 1,100,000
Vested (in dollars)			1,000,000
Compensation cost not yet recognized			1,400,000
Range of payout of shares for each executive, minimum				0.00%	0.00%
Range of payout of shares for each executive, maximum				150.00%	150.00%
Restricted Stock Units and Restricted Stock Awards [Member]
Tax benefit from compensation expense			1,900,000	$ 1,500,000	$ 2,000,000
Allocated share-based compensation expense			8,000,000	8,600,000	10,100,000
Compensation cost not yet recognized			$ 8,800,000
Period for recognition			1 year 9 months 18 days
Fair value of shares vested			$ 10,400,000	$ 3,900,000	$ 8,100,000
Restricted Stock Units and Restricted Stock Awards [Member] | Minimum [Member]
Vesting period				3 years
Restricted Stock Units and Restricted Stock Awards [Member] | Maximum [Member]
Vesting period				4 years
Time Based Restricted Stock Units [Member]
Allocated share-based compensation expense		$ 5,300,000
Range of payout of shares for each executive, minimum			0.00%
Range of payout of shares for each executive, maximum			150.00%
The 2014 Director Plan [Member]
Number of shares authorized | shares			1,000,000
Shares available for grant | shares			504,258
The 2014 Director Plan [Member] | Non-employee Directors [Member]
Restricted shares granted	$ 150,000
The 2014 Director Plan [Member] | Non-employee Directors [Member] | Restricted stock [Member]
Granted, restricted stock | shares			98,714
Estimated fair value at date of grant (in dollars per share) | $ / shares			$ 7.80
The 2014 Director Plan [Member] | Board of Directors Chairman [Member]
Restricted shares granted	$ 170,000
2015 Plan [Member]
Number of shares authorized | shares						9,800,000	7,800,000	6,000,000
Shares available for grant | shares			2,079,603
2015 Plan [Member] | Full Value Awards [Member]
Shares available for grant reduction rate			1.78
2015 Plan [Member] | Grants of Stock Options and Stock Appreciation Rights [Member]
Shares available for grant reduction rate			1.00
Participants Contributions Up to 3 Percent of Compensation [Member]
Employer matching contribution, percent of employees' gross pay			3.00%
Employer matching contribution, percent of match			100.00%
Participants Contributions from 3 Percent to 6 Percent of Compensation [Member]
Options granted | shares			0
Employer matching contribution, percent of match			50.00%
Participants Contributions from 3 Percent to 6 Percent of Compensation [Member] | Minimum [Member]
Employer matching contribution, percent of employees' gross pay			3.00%
Participants Contributions from 3 Percent to 6 Percent of Compensation [Member] | Maximum [Member]
Employer matching contribution, percent of employees' gross pay			6.00%