Condensed Guarantor and Non-Guarantor Financial Information, Cash Flow Statements (Details) - USD ($) $ in Millions		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018
Condensed Financial Statements, Captions
Proceeds from disposition of property, plant and equipment		$ 0.2	$ 0.0
Cash flows from operating activities:
Net cash (used in) provided by operating activities		70.5	84.0
Cash flows from investing activities
Capital expenditures		(29.9)	(35.8)
Purchase of available for sale securities		(33.0)	(24.0)
Payments to Acquire Available-for-sale Securities, Equity		(0.7)	(0.9)
Proceeds from disposition of available for sale securities		45.7	136.6
Intercompany loans receivable		0.0	0.0
Net cash (used in) provided by investing activities	[1]	(17.7)	75.9
Cash flows from financing activities
Repayment of finance lease		(0.6)	(0.3)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(6.2)	(6.9)
Repurchase of common stock		(28.6)	(18.9)
Cash dividends paid to Parent			0.0
Cash dividends and dividend equivalents paid		(20.1)	(19.3)
Intercompany loans payable		0.0	0.0
Net cash used in financing activities	[1]	(55.5)	(45.4)
Net increase in cash, cash equivalents, and restricted cash during the period		(2.7)	114.5
Cash, cash equivalents and restricted cash at beginning of period		139.6	64.3
Cash, cash equivalents and restricted cash at end of period		136.9	178.8
Consolidating Adjustments
Condensed Financial Statements, Captions
Proceeds from disposition of property, plant and equipment		0.0
Cash flows from operating activities:
Net cash (used in) provided by operating activities		0.0	(100.0)
Cash flows from investing activities
Capital expenditures		0.0	0.0
Purchase of available for sale securities		0.0	0.0
Payments to Acquire Available-for-sale Securities, Equity		0.0	0.0
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		(68.5)	41.7
Net cash (used in) provided by investing activities		(68.5)	41.7
Cash flows from financing activities
Repayment of finance lease		0.0	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		0.0	0.0
Repurchase of common stock		0.0	0.0
Cash dividends paid to Parent			100.0
Cash dividends and dividend equivalents paid		0.0	0.0
Intercompany loans payable		68.5	(41.7)
Net cash used in financing activities		68.5	58.3
Net increase in cash, cash equivalents, and restricted cash during the period		0.0	0.0
Cash, cash equivalents and restricted cash at beginning of period		0.0	0.0
Cash, cash equivalents and restricted cash at end of period		0.0	0.0
Parent
Condensed Financial Statements, Captions
Proceeds from disposition of property, plant and equipment		0.0
Cash flows from operating activities:
Net cash (used in) provided by operating activities		(14.8)	87.9
Cash flows from investing activities
Capital expenditures		0.0	0.0
Purchase of available for sale securities		0.0	0.0
Payments to Acquire Available-for-sale Securities, Equity		0.0	0.0
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		69.7	(42.8)
Net cash (used in) provided by investing activities		69.7	(42.8)
Cash flows from financing activities
Repayment of finance lease		0.0	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(6.2)	(6.9)
Repurchase of common stock		(28.6)	(18.9)
Cash dividends paid to Parent			0.0
Cash dividends and dividend equivalents paid		(20.1)	(19.3)
Intercompany loans payable		0.0	0.0
Net cash used in financing activities		(54.9)	(45.1)
Net increase in cash, cash equivalents, and restricted cash during the period		0.0	0.0
Cash, cash equivalents and restricted cash at beginning of period		0.0	0.0
Cash, cash equivalents and restricted cash at end of period		0.0	0.0
Guarantor Subsidiaries
Condensed Financial Statements, Captions
Proceeds from disposition of property, plant and equipment		0.2
Cash flows from operating activities:
Net cash (used in) provided by operating activities		85.0	96.3
Cash flows from investing activities
Capital expenditures		(29.0)	(35.2)
Purchase of available for sale securities		(33.0)	(24.0)
Payments to Acquire Available-for-sale Securities, Equity		(0.7)	(0.9)
Proceeds from disposition of available for sale securities		45.7	136.6
Intercompany loans receivable		(0.4)	0.0
Net cash (used in) provided by investing activities		(17.2)	76.5
Cash flows from financing activities
Repayment of finance lease		(0.6)	(0.3)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		0.0	0.0
Repurchase of common stock		0.0	0.0
Cash dividends paid to Parent			(100.0)
Cash dividends and dividend equivalents paid		0.0	0.0
Intercompany loans payable		(68.6)	41.7
Net cash used in financing activities		(69.2)	(58.6)
Net increase in cash, cash equivalents, and restricted cash during the period		(1.4)	114.2
Cash, cash equivalents and restricted cash at beginning of period		136.3	61.3
Cash, cash equivalents and restricted cash at end of period		134.9	175.5
Non-Guarantor Subsidiaries
Condensed Financial Statements, Captions
Proceeds from disposition of property, plant and equipment		0.0
Cash flows from operating activities:
Net cash (used in) provided by operating activities		0.3	(0.2)
Cash flows from investing activities
Capital expenditures		(0.9)	(0.6)
Purchase of available for sale securities		0.0	0.0
Payments to Acquire Available-for-sale Securities, Equity		0.0	0.0
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		(0.8)	1.1
Net cash (used in) provided by investing activities		(1.7)	0.5
Cash flows from financing activities
Repayment of finance lease		0.0	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		0.0	0.0
Repurchase of common stock		0.0	0.0
Cash dividends paid to Parent			0.0
Cash dividends and dividend equivalents paid		0.0	0.0
Intercompany loans payable		0.1	0.0
Net cash used in financing activities		0.1	0.0
Net increase in cash, cash equivalents, and restricted cash during the period		(1.3)	0.3
Cash, cash equivalents and restricted cash at beginning of period		3.3	3.0
Cash, cash equivalents and restricted cash at end of period		$ 2.0	$ 3.3

[1] See Note 12 for supplemental cash flow information.