Stockholders' Equity (Schedule of Stock by Class) (Details) $ in Millions	Dec. 31, 2015 USD ($) occasion
Registration Rights Agreement, Other Than Form S-3
Demand registration rights
Minimum ownership of outstanding shares for holders to exercise demand registration rights (as a percent)	25.00%
Minimum offering relative to outstanding shares to trigger demand registration rights (as a percent)	20.00%
Minimum aggregate offering price to trigger demand registration rights | $	$ 20
Maximum number of registration statements under demand registration rights | occasion	2
Registration Rights Agreement, Form S-3
Demand registration rights
Minimum ownership of outstanding shares for holders to exercise demand registration rights (as a percent)	25.00%
Minimum offering relative to outstanding shares to trigger demand registration rights (as a percent)	25.00%
Minimum aggregate offering price to trigger demand registration rights | $	$ 5
Maximum number of registration statements under demand registration rights | occasion	1