Long-Term Debt - Convertible Notes Embedded Derivative (Details) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended		12 Months Ended
	Jul. 31, 2014 shares	Jun. 30, 2014 USD ($) shares	Sep. 30, 2016 day $ / shares
2.125% Cash convertible senior notes due 2019
Debt Instrument [Line Items]
Repurchase price, percent of principal amount			100.00%
2.125% Cash convertible senior notes due 2019 | Common Class A
Debt Instrument [Line Items]
Conversion rate per $1000 principal amount			62.2471
Conversion price, per share (in dollars per share) | $ / shares			$ 16.065
Trading day observation period			80 days
Threshold trading days (whether or not consecutive) | day			20
Threshold consecutive trading days			30 days
Threshold percentage of stock price trigger			130.00%
Early conversion condition, business day period			5 days
Measurement period			5 days
Early conversion condition, percent of product of the last reported sale price of stock			98.00%
Convertible Notes Embedded Derivative | Long-term debt, less current maturities
Debt Instrument [Line Items]
Fair value, derivative liability | $		$ 46.5
Convertible Notes Hedges | Common Class A
Debt Instrument [Line Items]
Stock repurchased (shares) | shares		1.0
Stock repurchased | $		$ 11.9
Treasury stock retired (shares) | shares	1.0