Stock-Based Compensation (Details 3) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Disclosures
Total unrecognized compensation cost related to the unvested awards	$ 21.1
Total weighted average remaining term of unvested awards	1 year 7 months 6 days
Compensation cost recognized	$ 10.9	$ 8.6	$ 9.6
Performance stock units
Summary of unvested restricted stock and deferred shares activity and related information
Unvested at beginning of year (in shares)	107
Granted (in shares)	106	117
Cancelled/Forfeitures (in shares)	(12)	(10)
Unvested at end of year (in shares)	201	107
Weighted Average Grant Date Fair Value
Unvested at beginning of period (in dollars per share)	$ 56.97
Granted (in dollars per share)	58.94	$ 57.02
Cancelled/Forfeitures (in dollars per share)	57.51	57.47
Unvested at end of period (in dollars per share)	$ 57.98	$ 56.97
Other Disclosures
Total unrecognized compensation cost related to the unvested awards	$ 7.9
Total weighted average remaining term of unvested awards	1 year 6 months 7 days
Compensation cost recognized	$ 1.7
Aggregate intrinsic value of restricted stock granted and outstanding	$ 0.0
Performance stock units | Class A
Other Disclosures
Company's closing Common Stock price (in dollars per share)	$ 49.67
Second Amended and Restated 2004 Stock Incentive Plan | Restricted stock and deferred shares
Summary of unvested restricted stock and deferred shares activity and related information
Unvested at beginning of year (in shares)	214	260	237
Granted (in shares)	180	151	142
Cancelled/Forfeitures (in shares)	(28)	(95)	(16)
Vested (in shares)	(122)	(102)	(103)
Unvested at end of year (in shares)	244	214	260
Weighted Average Grant Date Fair Value
Unvested at beginning of period (in dollars per share)	$ 53.74	$ 45.58	$ 35.45
Granted (in dollars per share)	50.87	56.79	54.80
Cancelled/Forfeitures (in dollars per share)	53.99	46.83	37.44
Vested (in dollars per share)	51.72	44.87	35.25
Unvested at end of period (in dollars per share)	$ 52.61	$ 53.74	$ 45.58
Other Disclosures
Total fair value of shares vested	$ 6.6	$ 5.9	$ 5.6
Total unrecognized compensation cost related to the unvested awards	$ 9.8
Total weighted average remaining term of unvested awards	1 year 9 months 18 days
Compensation cost recognized	$ 6.7	$ 4.8	$ 5.1
Aggregate intrinsic value of restricted stock granted and outstanding	$ 10.9
Second Amended and Restated 2004 Stock Incentive Plan | Restricted stock and deferred shares | Class A
Other Disclosures
Company's closing Common Stock price (in dollars per share)	$ 49.67
Management Stock Purchase Plan | Restricted stock | Class A
Other Disclosures
Company's closing Common Stock price (in dollars per share)	$ 49.67
Management Stock Purchase Plan | Restricted stock units (RSUs)
Summary of unvested restricted stock and deferred shares activity and related information
Granted (in shares)	60	31	45
Cancelled/Forfeitures (in shares)	(9)	(32)	(14)
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 19.04	$ 22.57	$ 18.05
Other Disclosures
Total unrecognized compensation cost related to the unvested awards	$ 0.9
Total weighted average remaining term of unvested awards	1 year 9 months 18 days
Compensation cost recognized	$ 0.6	$ 0.5	$ 0.7
Dividend declared and unpaid	$ 0.1