Consolidated Statements of Operations - USD ($) shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Consolidated Statements of Operations
Revenue	$ 192.7	$ 181.8	$ 175.5	$ 175.4	$ 181.7	$ 173.3	$ 178.0	$ 169.4	$ 725.4	$ 702.4	$ 654.6
Costs and expenses:
Cost of revenue, excluding depreciation and amortization	51.9	39.9	38.1	34.5	34.1	34.3	37.2	39.3	164.4	144.9	162.3
Selling, general and administrative	49.4	46.5	42.8	46.4	47.5	49.6	52.9	57.0	185.1	207.0	219.6
Depreciation and amortization	64.7	64.6	66.9	71.0	74.3	70.4	68.7	67.3	267.2	280.7	239.7
Restructuring charges	1.1	1.0	1.6	2.9	6.0	0.4	0.4	2.2	6.6	9.0	1.1
Income from operations	25.6	29.8	26.1	20.6	19.8	18.6	18.8	3.6	102.1	60.8	31.9
Loss from early extinguishment of debt	(35.7)								(35.7)
Interest expense, net	(4.0)	(4.0)	(4.7)	(5.1)	(5.3)	(5.6)	(5.4)	(12.7)	(17.8)	(29.0)	(7.1)
Other income, net	0.1					1.6			0.1	1.6	0.6
Income before income taxes	(14.0)	25.8	21.4	15.5	14.5	14.6	13.4	(9.1)	48.7	33.4	25.4
Income tax expense	5.1	(9.5)	(7.9)	(6.0)	(3.4)	(4.6)	(5.4)	4.2	(18.3)	(9.2)	(6.9)
Equity in earnings from joint ventures, net of tax	(0.4)	(1.3)	(1.3)	(0.9)	(0.5)	(0.4)			(3.9)	(0.9)
Net income	(9.3)	15.0	12.2	8.6	10.6	9.6	8.0	(4.9)	26.5	23.3	18.5
Preferred stock dividends	(1.0)	(1.0)	(1.0)	(1.0)	(1.0)	(1.0)	(1.0)	(1.0)	(4.0)	(4.0)	(4.0)
Net income less preferred stock dividends	(10.3)	14.0	11.2	7.6	9.6	8.6	7.0	(5.9)	22.5	19.3	14.5
Income allocated to participating securities		0.7	0.5	0.3	0.4	0.4	0.3		1.0	0.8	0.6
Net income available to common stockholders	$ (10.3)	$ 13.3	$ 10.7	$ 7.3	$ 9.2	$ 8.2	$ 6.7	$ (5.9)	$ 21.5	$ 18.5	$ 13.9
Earnings per share:
Basic earnings per share (in dollars per share)	$ (0.17)	$ 0.21	$ 0.17	$ 0.11	$ 0.13	$ 0.12	$ 0.09	$ (0.08)	$ 0.34	$ 0.26	$ 0.19
Diluted earnings per share (in dollars per share)	$ (0.17)	$ 0.21	$ 0.17	$ 0.11	$ 0.13	$ 0.12	$ 0.09	$ (0.08)	$ 0.34	$ 0.26	$ 0.18
Weighted average common shares outstanding:
Basic (in shares)									63.1	71.0	74.9
Diluted (in shares)									63.8	71.5	75.9