Stock-Based Compensation Plans - Restricted Stock Awards and Performance-Based Restricted Stock Units (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested shares at December 31 (in shares)	772,000	1,009,000	957,000
Granted (in shares)	84,000	332,000	559,000
Vested and transferred to unrestricted common stock (in shares)	(341,000)	(403,000)	(429,000)
Forfeited (in shares)	(68,000)	(166,000)	(78,000)
Nonvested shares at December 31 (in shares)	447,000	772,000	1,009,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested shares at December 31 (USD per share)	$ 8.98	$ 7.92	$ 7.66
Granted (USD per share)	9.37	11.00	8.24
Vested and transferred to unrestricted common stock (USD per share)	8.83	8.28	7.71
Forfeited (USD per share)	9.29	8.51	8.04
Nonvested shares at December 31 (USD per share)	$ 9.13	$ 8.98	$ 7.92
Phantom Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Expense	$ (0.4)	$ 0.4
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested shares at December 31 (in shares)	128,234	0
Granted (in shares)	186,784	151,822
Forfeited (in shares)	(21,731)	(23,588)
Nonvested shares at December 31 (in shares)	293,287	128,234	0
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested shares at December 31 (USD per share)	$ 11.10	$ 0.00
Granted (USD per share)	7.36	11.10
Forfeited (USD per share)	11.10	11.10
Nonvested shares at December 31 (USD per share)	$ 8.72	$ 11.10	$ 0.00
Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	7.00%
Minimum | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Minimum | Phantom Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	0
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage	8.00%
Maximum | Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Maximum | Phantom Share Units (PSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance	586,574