Stockholders' Deficit - Stock Repurchase Program (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Jan. 28, 2015	Jan. 27, 2015	Apr. 23, 2014
Stockholders' Deficit
Approved stock repurchase program, authorized amount				$ 450.0		$ 200.0
Repurchase of common stock (in shares)	0	1,339,499	7,731,428
Repurchase of common stock, amount		$ 55.1	$ 298.3
Remaining capacity under the stock repurchase program	$ 246.3				$ 25.4