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)	Class A Common Stock	Class B Common Stock
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)
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)
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
Increase (Decrease) in Stockholders' Equity
Comprehensive income (loss)	76.6		68.4	8.2
Shares of Class B Common Stock converted to Class A Common Stock					0.1	(0.1)
Shares of Class B Common Stock converted to Class A Common Stock (in shares)					365,000	(365,000)
Shares of Class A Common Stock issued upon the exercise of stock options	17.8	17.7			0.1
Shares of Class A Common Stock issued upon the exercise of stock options (in shares)					589,798
Stock-based compensation	6.6	6.6
Stock repurchase	(65.8)		(65.6)		(0.2)
Stock repurchase (in shares)					(2,000,000)
Issuance of net shares of restricted Class A Common Stock	(0.8)		(0.8)
Issuance of net shares of restricted Class A Common Stock (in shares)					141,767
Net change in restricted stock units	1.3	4.3	(3.0)
Net change in restricted stock units (in shares)					105,660
Common Stock dividends	(16.0)		(16.0)
Balance at Dec. 31, 2012	$ 939.5	$ 448.7	$ 498.1	$ (10.8)	$ 2.9	$ 0.6
Balance (in shares) at Dec. 31, 2012					28,673,639	6,588,680