Condensed Guarantor and Non-Guarantor Financial Information, Cash Flow Statements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net cash (used in) provided by operating activities				$ 131.5	$ 107.4
Cash flows from investing activities
Capital expenditures		$ (16.4)	$ (15.1)	(56.1)	(57.4)
Purchase of available for sale securities				(196.0)	(201.1)
Proceeds from disposition of available for sale securities				237.2	30.0
Proceeds from disposal of property, plant and equipment				0.6	0.0
Intercompany loans receivable				0.0	0.0
Net cash used in investing activities	[1]			(14.3)	(228.5)
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				0.0	(206.0)
Issuance of 5.875% Senior Notes				0.0	375.0
Cash paid for debt issuance costs				0.0	(6.8)
Proceeds from stock option exercises				0.0	1.0
Repayment of capital lease				(0.2)	(0.1)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares				(4.5)	(2.8)
Repurchase of common stock				(66.7)	(13.6)
Cash dividends and dividend equivalents paid				(26.4)	(24.4)
Cash dividends paid to Parent					0.0
Intercompany loans payable				0.0	0.0
Net cash (used in) provided by financing activities	[1]			(97.8)	122.3
Net increase in cash, cash equivalents and restricted cash during the period				19.4	1.2
Cash, cash equivalents and restricted cash at beginning of period				67.7	83.7
Cash, cash equivalents and restricted cash at end of period		87.1	84.9	87.1	84.9
Consolidating Adjustments
Cash flows from operating activities:
Net cash (used in) provided by operating activities				0.0	(200.0)
Cash flows from investing activities
Capital expenditures				0.0	0.0
Purchase of available for sale securities				0.0	0.0
Proceeds from disposition of available for sale securities				0.0	0.0
Proceeds from disposal of property, plant and equipment				0.0
Intercompany loans receivable				(104.8)	103.3
Net cash used in investing activities				(104.8)	103.3
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes					0.0
Issuance of 5.875% Senior Notes					0.0
Cash paid for debt issuance costs					0.0
Proceeds from stock option exercises					0.0
Repayment of capital 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 and dividend equivalents paid				0.0	0.0
Cash dividends paid to Parent					200.0
Intercompany loans payable				104.8	(103.3)
Net cash (used in) provided by financing activities				104.8	96.7
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	0.0	0.0
Parent
Cash flows from operating activities:
Net cash (used in) provided by operating activities				(12.8)	189.7
Cash flows from investing activities
Capital expenditures				0.0	0.0
Purchase of available for sale securities				0.0	0.0
Proceeds from disposition of available for sale securities				0.0	0.0
Proceeds from disposal of property, plant and equipment				0.0
Intercompany loans receivable				110.4	(205.6)
Net cash used in investing activities				110.4	(205.6)
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes					(206.0)
Issuance of 5.875% Senior Notes					375.0
Cash paid for debt issuance costs					(6.8)
Proceeds from stock option exercises					1.0
Repayment of capital lease				0.0	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares				(4.5)	(2.8)
Repurchase of common stock				(66.7)	(13.6)
Cash dividends and dividend equivalents paid				(26.4)	(24.4)
Cash dividends paid to Parent					0.0
Intercompany loans payable				0.0	(106.5)
Net cash (used in) provided by financing activities				(97.6)	15.9
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	0.0	0.0
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash (used in) provided by operating activities				137.4	109.3
Cash flows from investing activities
Capital expenditures				(55.7)	(55.6)
Purchase of available for sale securities				(196.0)	(201.1)
Proceeds from disposition of available for sale securities				237.2	30.0
Proceeds from disposal of property, plant and equipment				0.6
Intercompany loans receivable				0.0	106.0
Net cash used in investing activities				(13.9)	(120.7)
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes					0.0
Issuance of 5.875% Senior Notes					0.0
Cash paid for debt issuance costs					0.0
Proceeds from stock option exercises					0.0
Repayment of capital lease				(0.2)	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 and dividend equivalents paid				0.0	0.0
Cash dividends paid to Parent					(200.0)
Intercompany loans payable				(104.8)	209.3
Net cash (used in) provided by financing activities				(105.0)	9.3
Net increase in cash, cash equivalents and restricted cash during the period				18.5	(2.1)
Cash, cash equivalents and restricted cash at beginning of period				65.1	83.0
Cash, cash equivalents and restricted cash at end of period		83.6	80.9	83.6	80.9
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash (used in) provided by operating activities				6.9	8.4
Cash flows from investing activities
Capital expenditures				(0.4)	(1.8)
Purchase of available for sale securities				0.0	0.0
Proceeds from disposition of available for sale securities				0.0	0.0
Proceeds from disposal of property, plant and equipment				0.0
Intercompany loans receivable				(5.6)	(3.7)
Net cash used in investing activities				(6.0)	(5.5)
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes					0.0
Issuance of 5.875% Senior Notes					0.0
Cash paid for debt issuance costs					0.0
Proceeds from stock option exercises					0.0
Repayment of capital lease				0.0	(0.1)
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 and dividend equivalents paid				0.0	0.0
Cash dividends paid to Parent					0.0
Intercompany loans payable				0.0	0.5
Net cash (used in) provided by financing activities				0.0	0.4
Net increase in cash, cash equivalents and restricted cash during the period				0.9	3.3
Cash, cash equivalents and restricted cash at beginning of period				2.6	0.7
Cash, cash equivalents and restricted cash at end of period		$ 3.5	$ 4.0	$ 3.5	$ 4.0

[1] See Note 12 for the supplemental disclosure on non-cash transactions.