Condensed Guarantor and Non-Guarantor Financial Information, Cash Flow Statements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2017	Mar. 31, 2016
Cash flows from operating activities:
Net cash (used in) provided by operating activities		$ 4.1	$ 21.3
Cash flows from investing activities
Capital expenditures		(14.8)	(25.9)
Purchase of available for sale securities		(74.7)	0.0
Proceeds from disposition of available for sale securities		110.9	20.0
Intercompany loans receivable		0.0
Net cash provided by (used in) investing activities	[1]	21.4	(5.9)
Cash flows from financing activities
Repayment of capital lease		(0.2)	0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(4.4)	(2.7)
Repurchase of common stock		(32.6)	(6.3)
Cash dividends and dividend equivalents paid		(9.3)	(8.2)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries			0.0
Intercompany loan			0.0
Change in Intercompany Loans Payable		0.0
Net cash used in financing activities	[1]	(46.5)	(17.2)
Net decrease in cash, cash equivalents and restricted cash during the period		(21.0)	(1.8)
Cash, cash equivalents and restricted cash at beginning of period		67.7	83.7
Cash, cash equivalents and restricted cash at end of period		46.7	81.9
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
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		(47.3)
Net cash provided by (used in) investing activities		(47.3)	0.0
Cash flows from financing activities
Repayment of capital lease		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 Company by Consolidated Subsidiaries			(200.0)
Intercompany loan			0.0
Change in Intercompany Loans Payable		47.3
Net cash used in financing activities		47.3	200.0
Net decrease 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
Cash flows from operating activities:
Net cash (used in) provided by operating activities		(0.3)	17.2
Cash flows from investing activities
Capital expenditures		0.0	0.0
Purchase of available for sale securities		0.0
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		46.6
Net cash provided by (used in) investing activities		46.6	0.0
Cash flows from financing activities
Repayment of capital lease		0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(4.4)	(2.7)
Repurchase of common stock		(32.6)	(6.3)
Cash dividends and dividend equivalents paid		(9.3)	(8.2)
Cash Dividends Paid to Parent Company by Consolidated Subsidiaries			0.0
Intercompany loan			0.0
Change in Intercompany Loans Payable		0.0
Net cash used in financing activities		(46.3)	(17.2)
Net decrease 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
Cash flows from operating activities:
Net cash (used in) provided by operating activities		2.6	201.4
Cash flows from investing activities
Capital expenditures		(14.7)	(25.3)
Purchase of available for sale securities		(74.7)
Proceeds from disposition of available for sale securities		110.9	20.0
Intercompany loans receivable		0.0
Net cash provided by (used in) investing activities		21.5	(5.3)
Cash flows from financing activities
Repayment of capital lease		(0.2)
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 Company by Consolidated Subsidiaries			200.0
Intercompany loan			0.8
Change in Intercompany Loans Payable		(47.3)
Net cash used in financing activities		(47.5)	(199.2)
Net decrease in cash, cash equivalents and restricted cash during the period		(23.4)	(3.1)
Cash, cash equivalents and restricted cash at beginning of period		65.1	83.0
Cash, cash equivalents and restricted cash at end of period		41.7	79.9
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash (used in) provided by operating activities		1.8	2.7
Cash flows from investing activities
Capital expenditures		(0.1)	(0.6)
Purchase of available for sale securities		0.0
Proceeds from disposition of available for sale securities		0.0	0.0
Intercompany loans receivable		0.7
Net cash provided by (used in) investing activities		0.6	(0.6)
Cash flows from financing activities
Repayment of capital lease		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 Company by Consolidated Subsidiaries			0.0
Intercompany loan			(0.8)
Change in Intercompany Loans Payable		0.0
Net cash used in financing activities		0.0	(0.8)
Net decrease in cash, cash equivalents and restricted cash during the period		2.4	1.3
Cash, cash equivalents and restricted cash at beginning of period		2.6	0.7
Cash, cash equivalents and restricted cash at end of period		$ 5.0	$ 2.0

[1] See Note 11 for the supplemental disclosure on non-cash transactions.