CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Adjustments related to tax withholding for share-based compensation	$ 3.6	$ 2.3	$ 2.7
Shares paid for tax withholding for share based compensation	487,559	309,206	345,559
Preferred Stock, Cumulative Redeemable - dividend rate (as a percent)	7.50%	7.50%
Preferred Stock | Series B Preferred Stock
Preferred Stock, Cumulative Redeemable - dividend rate (as a percent)	7.50%
Preferred Stock, Cumulative Redeemable - Liquidation Preference per Share (in dollars per share)	$ 25.00