Consolidated Statements of Stockholders' Equity (USD $) In Millions, except Share data, unless otherwise specified	Total	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Comprehensive Income	Class A	Class A Common Stock	Class B Common Stock
Balance at Dec. 31, 2008	$ 842.4	$ 386.9	$ 451.7	$ 0.2			$ 2.9	$ 0.7
Balance (in shares) at Dec. 31, 2008							29,250,175	7,293,880
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	47.3		17.4	29.9	47.3
Shares of Class B Common Stock converted to Class A Common Stock (in shares)							100,000	(100,000)
Shares of Class A Common Stock issued upon the exercise of stock options	0.5	0.4					0.1
Shares of Class A Common Stock issued upon the exercise of stock options (in shares)							30,194
Stock-based compensation	4.9	4.9
Issuance of net shares of restricted Class A Common Stock	(0.4)		(0.4)
Issuance of net shares of restricted Class A Common Stock (in shares)							58,454
Net change in restricted stock units	1.1	1.5	(0.4)
Net change in restricted stock units (in shares)							67,700
Common Stock dividends	(16.2)		(16.2)
Balance at Dec. 31, 2009	879.6	393.7	452.1	30.1			3.0	0.7
Balance (in shares) at Dec. 31, 2009							29,506,523	7,193,880
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	28.4		58.8	(30.4)	28.4
Shares of Class B Common Stock converted to Class A Common Stock (in shares)							240,200	(240,200)
Shares of Class A Common Stock issued upon the exercise of stock options	3.4	3.4
Shares of Class A Common Stock issued upon the exercise of stock options (in shares)							185,470
Stock-based compensation	4.7	4.7
Issuance of net shares of restricted Class A Common Stock	(0.5)		(0.5)
Issuance of net shares of restricted Class A Common Stock (in shares)							93,601
Net change in restricted stock units	2.3	3.4	(1.1)
Net change in restricted stock units (in shares)							76,883
Common Stock dividends	(16.4)		(16.4)
Balance at Dec. 31, 2010	901.5	405.2	492.9	(0.3)			3.0	0.7
Balance (in shares) at Dec. 31, 2010							30,102,677	6,953,680
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	47.7		66.4	(18.7)	47.7
Shares of Class A Common Stock issued upon the exercise of stock options	5.4	5.4
Shares of Class A Common Stock issued upon the exercise of stock options (in shares)							247,870
Stock-based compensation	8.3	8.3
Stock repurchase	(27.2)		(27.1)				(0.1)
Stock repurchase (in shares)							(1,000,000)
Issuance of net shares of restricted Class A Common Stock	(0.5)		(0.5)
Issuance of net shares of restricted Class A Common Stock (in shares)							79,438
Net change in restricted stock units	0.9	1.2	(0.3)
Net change in restricted stock units (in shares)							41,429
Common Stock dividends	(16.3)		(16.3)
Balance at Dec. 31, 2011	$ 919.8	$ 420.1	$ 515.1	$ (19.0)			$ 2.9	$ 0.7
Balance (in shares) at Dec. 31, 2011							29,471,414	6,953,680