Condensed Guarantor and Non-Guarantor Financial Statements, Cash Flow Statements (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net cash provided by operating activities				$ 106.6	$ 108.9
Cash flows from investing activities
Capital expenditures		$ (15.1)	$ (15.5)	(57.4)	(38.4)
Purchase of available for sale securities				(201.1)	(0.5)
Proceeds from disposition of available for sale securities				30.0	84.0
Intercompany loans receivable				0.0
Net cash (used in) provided by investing activities	[1]			(228.5)	45.1
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				(206.0)	(6.1)
Issuance of 5.875% Senior Notes				375.0	0.0
Cash paid for debt issuance costs				(6.8)	0.0
Repayment of Convertible Notes				0.0	(175.0)
Proceeds from cash-settled call options related to repayment of Convertible Notes				0.0	94.9
Payment for conversion premium related to repayment of Convertible Notes				0.0	(94.9)
Proceeds from stock option exercises				1.0	0.0
Repayment of capital lease				(0.1)	0.0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	[2]			0.0	1.1
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares				(2.8)	(3.0)
Repurchase of common stock				(13.6)	(45.1)
Cash dividends paid to stockholders				(24.4)	(21.0)
Intercompany loans payable					0.0
Cash dividends paid to Parent				0.0
Change in Intercompany Loans Payable				0.0
Net cash provided by (used in) financing activities	[1]			122.3	(249.1)
Net (decrease) increase in cash and cash equivalents during the period				0.4	(95.1)
Cash and cash equivalents at beginning of period			82.6	72.5	177.7
Cash and cash equivalents at end of period		72.9	82.6	72.9	82.6
Consolidating Adjustments
Cash flows from operating activities:
Net cash provided by operating activities				(200.0)	0.0
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
Intercompany loans receivable				103.3
Net cash (used in) provided by investing activities				103.3	0.0
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				0.0	0.0
Issuance of 5.875% Senior Notes				0.0
Cash paid for debt issuance costs				0.0
Repayment of Convertible Notes					0.0
Proceeds from cash-settled call options related to repayment of Convertible Notes					0.0
Payment for conversion premium related to repayment of Convertible Notes					0.0
Proceeds from stock option exercises				0.0
Repayment of capital lease				0.0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest					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 stockholders				0.0	0.0
Intercompany loans payable					0.0
Cash dividends paid to Parent				200.0
Change in Intercompany Loans Payable				(103.3)
Net cash provided by (used in) financing activities				96.7	0.0
Net (decrease) increase in cash and cash equivalents during the period				0.0	0.0
Cash and cash equivalents at beginning of period				0.0	0.0
Cash and cash equivalents at end of period		0.0	0.0	0.0	0.0
Parent
Cash flows from operating activities:
Net cash provided by operating activities				189.7	250.2
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
Intercompany loans receivable				(205.6)
Net cash (used in) provided by investing activities				(205.6)	0.0
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				(206.0)	(6.1)
Issuance of 5.875% Senior Notes				375.0
Cash paid for debt issuance costs				(6.8)
Repayment of Convertible Notes					(175.0)
Proceeds from cash-settled call options related to repayment of Convertible Notes					94.9
Payment for conversion premium related to repayment of Convertible Notes					(94.9)
Proceeds from stock option exercises				1.0
Repayment of capital lease				0.0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest					0.0
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares				(2.8)	(3.0)
Repurchase of common stock				(13.6)	(45.1)
Cash dividends paid to stockholders				(24.4)	(21.0)
Intercompany loans payable					0.0
Cash dividends paid to Parent				0.0
Change in Intercompany Loans Payable				(106.5)
Net cash provided by (used in) financing activities				15.9	(250.2)
Net (decrease) increase in cash and cash equivalents during the period				0.0	0.0
Cash and cash equivalents at beginning of period				0.0	0.0
Cash and cash equivalents at end of period		0.0	0.0	0.0	0.0
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash provided by operating activities				108.4	(140.8)
Cash flows from investing activities
Capital expenditures				(55.6)	(26.0)
Purchase of available for sale securities				(201.1)	(0.5)
Proceeds from disposition of available for sale securities				30.0	84.0
Intercompany loans receivable				106.0
Net cash (used in) provided by investing activities				(120.7)	57.5
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				0.0	0.0
Issuance of 5.875% Senior Notes				0.0
Cash paid for debt issuance costs				0.0
Repayment of Convertible Notes					0.0
Proceeds from cash-settled call options related to repayment of Convertible Notes					0.0
Payment for conversion premium related to repayment of Convertible Notes					0.0
Proceeds from stock option exercises				0.0
Repayment of capital lease				0.0
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest					1.1
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 paid to stockholders				0.0	0.0
Intercompany loans payable					(13.5)
Cash dividends paid to Parent				(200.0)
Change in Intercompany Loans Payable				209.3
Net cash provided by (used in) financing activities				9.3	(12.4)
Net (decrease) increase in cash and cash equivalents during the period				(3.0)	(95.7)
Cash and cash equivalents at beginning of period				72.2	175.3
Cash and cash equivalents at end of period		69.2	79.6	69.2	79.6
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash provided by operating activities				8.5	(0.5)
Cash flows from investing activities
Capital expenditures				(1.8)	(12.4)
Purchase of available for sale securities				0.0	0.0
Proceeds from disposition of available for sale securities				0.0	0.0
Intercompany loans receivable				(3.7)
Net cash (used in) provided by investing activities				(5.5)	(12.4)
Cash flows from financing activities
Repayment of principal and redemption premium of 8.25% Senior Notes				0.0	0.0
Issuance of 5.875% Senior Notes				0.0
Cash paid for debt issuance costs				0.0
Repayment of Convertible Notes					0.0
Proceeds from cash-settled call options related to repayment of Convertible Notes					0.0
Payment for conversion premium related to repayment of Convertible Notes					0.0
Proceeds from stock option exercises				0.0
Repayment of capital lease				(0.1)
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest					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 stockholders				0.0	0.0
Intercompany loans payable					13.5
Cash dividends paid to Parent				0.0
Change in Intercompany Loans Payable				0.5
Net cash provided by (used in) financing activities				0.4	13.5
Net (decrease) increase in cash and cash equivalents during the period				3.4	0.6
Cash and cash equivalents at beginning of period				0.3	2.4
Cash and cash equivalents at end of period		$ 3.7	$ 3.0	$ 3.7	$ 3.0

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

[2] See Note 4 and Note 6 for discussion of our adoption of ASU 2016-09 (as defined in Note 1).