Equity, Stock Repurchase Program, Dividends, and Shelf Registration (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	11 Months Ended	12 Months Ended
	Dec. 31, 2015	Nov. 30, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Aug. 31, 2015	Apr. 30, 2015	Dec. 31, 1999
Dividends Payable [Line Items]
Dividends declared (in dollars per share)			$ 0.08	$ 0.28	$ 0.50
Share based compensation dividends accrued	$ 0.6		$ 0.4	$ 0.6
Debt Instrument [Line Items]
Amount available for issuance under shelf registration agreement							$ 500.0
Common Class A [Member] | Stock Repurchase Program [Member]
Stock Repurchase Program [Abstract]
Amount of shares authorized to be repurchased								$ 9.0
Number of shares authorized to be repurchased (in shares)						500,000
Shares repurchased (in shares)	13,400	413,228	348,687	426,628	414,432
Average price per share of repurchased shares (in dollars per share)	$ 32.56	$ 64.86	$ 30.88	$ 63.85	$ 78.99
Share available under program to repurchase (in shares)			233,468
Common Stock Class A and Class B [Member]
Dividends Payable [Line Items]
Dividends declared (in dollars per share)			$ 0.08	$ 0.28	$ 0.50
Dividend cost			$ 2.4	$ 7.5	$ 12.9