Guarantor and Non-Guarantor Financial Statements, Cash Flow Statements (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:
Net cash (used in) provided by operating activities	$ 71.3	$ 48.9
Cash flows from investing activities:
Capital expenditures	(30.1)	(26.0)
Purchase of available for sale securities	(23.4)	(98.2)
Proceeds from disposition of available for sale securities	25.0	135.7
Change in restricted cash	0	0.7
Net cash provided by (used in) investing activities	(28.5)	12.2
Cash flows from financing activities:
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.8	0.9
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	(2.4)	(2.2)
Repurchase of common stock	(23.7)	(39.9)
Cash dividend paid to stockholders	(12.8)	(11.6)
Intercompany loan	0	0
Net cash provided by (used in) financing activities	(38.1)	(52.8)
Net increase (decrease) in cash and cash equivalents during the period	4.7	8.3
Cash and cash equivalents at beginning of period	169.5	273.4
Cash and cash equivalents at end of period	174.2	281.7
Parent
Cash flows from operating activities:
Net cash (used in) provided by operating activities	7.6	(14.4)
Cash flows from investing activities:
Capital expenditures	0	0
Purchase of available for sale securities	0	0
Proceeds from disposition of available for sale securities	0	0
Change in restricted cash		0
Net cash provided by (used in) investing activities	0	0
Cash flows from financing activities:
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	(2.4)	(2.2)
Repurchase of common stock	(23.7)	(39.9)
Cash dividend paid to stockholders	(12.8)	(11.6)
Intercompany loan	31.3	68.1
Net cash provided by (used in) financing activities	(7.6)	14.4
Net increase (decrease) in cash and cash equivalents during the period	0	0
Cash and cash equivalents at beginning of period	5.0	5.0
Cash and cash equivalents at end of period	5.0	5.0
Guarantor Subsidiaries
Cash flows from operating activities:
Net cash (used in) provided by operating activities	56.9	60.4
Cash flows from investing activities:
Capital expenditures	(29.4)	(25.0)
Purchase of available for sale securities	(23.4)	(98.2)
Proceeds from disposition of available for sale securities	25.0	135.7
Change in restricted cash		0.7
Net cash provided by (used in) investing activities	(27.8)	13.2
Cash flows from financing activities:
Excess tax benefit upon vesting of non-vested shares and dividend payment on unvested shares expected to vest	0.8	0.9
Cancellation of shares to cover employees’ tax withholdings upon vesting of non-vested shares	0	0
Repurchase of common stock	0	0
Cash dividend paid to stockholders	0	0
Intercompany loan	(22.9)	(64.8)
Net cash provided by (used in) financing activities	(22.1)	(63.9)
Net increase (decrease) in cash and cash equivalents during the period	7.0	9.7
Cash and cash equivalents at beginning of period	157.7	266.0
Cash and cash equivalents at end of period	164.7	275.7
Non-Guarantor Subsidiaries
Cash flows from operating activities:
Net cash (used in) provided by operating activities	6.8	2.9
Cash flows from investing activities:
Capital expenditures	(0.7)	(1.0)
Purchase of available for sale securities	0	0
Proceeds from disposition of available for sale securities	0	0
Change in restricted cash		0
Net cash provided by (used in) investing activities	(0.7)	(1.0)
Cash flows from financing activities:
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
Repurchase of common stock	0	0
Cash dividend paid to stockholders	0	0
Intercompany loan	(8.4)	(3.3)
Net cash provided by (used in) financing activities	(8.4)	(3.3)
Net increase (decrease) in cash and cash equivalents during the period	(2.3)	(1.4)
Cash and cash equivalents at beginning of period	6.8	2.4
Cash and cash equivalents at end of period	4.5	1.0
Consolidating Adjustments
Cash flows from operating activities:
Net cash (used in) provided by operating activities	0	0
Cash flows from investing activities:
Capital expenditures	0	0
Purchase of available for sale securities	0	0
Proceeds from disposition of available for sale securities	0	0
Change in restricted cash		0
Net cash provided by (used in) investing activities	0	0
Cash flows from financing activities:
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
Repurchase of common stock	0	0
Cash dividend paid to stockholders	0	0
Intercompany loan	0	0
Net cash provided by (used in) financing activities	0	0
Net increase (decrease) in cash and cash equivalents during the period	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0