Equity - Narrative (Details) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended								12 Months Ended
	Mar. 31, 2007 Right	Dec. 31, 2015 $ / shares shares	Sep. 30, 2015 $ / shares	Jun. 30, 2015 $ / shares	Mar. 31, 2015 $ / shares	Dec. 31, 2014 $ / shares shares	Sep. 30, 2014 $ / shares	Jun. 30, 2014 $ / shares	Mar. 31, 2014 $ / shares	Dec. 31, 2015 USD ($) D $ / shares shares	Dec. 31, 2014 $ / shares shares	Dec. 31, 2013 $ / shares	Mar. 21, 2007 $ / shares
Equity [Abstract]
Authorized capitalization of common stock (in shares)		300,000,000				300,000,000				300,000,000	300,000,000
Par value of common stock (in dollars per share) | $ / shares		$ 0.01								$ 0.01			$ 0.01
Authorized capitalization of preferred stock (in shares)		3,500,000.0								3,500,000.0
Par value of preferred stock per share (in dollars per share) | $ / shares		$ 0.01								$ 0.01
Number of rights per common stock share distributed as dividends | Right	1
Number of shares of common stock the registered holder of each right is entitled to purchase when exercisable (in shares)		1								1
Purchase price of each common stock share following the exercise of rights (in dollars per share) | $ / shares		$ 110.00								$ 110.00
Rights exercisable after public announcement of an acquisition or right to acquire 20% or more of outstanding common stock shares (in number of days) | D										10
Beneficial ownership by a person or group of affiliated persons before rights become exercisable (as a percent) (or more)										20.00%
Rights exercisable after tender offer or exchange offer to acquire 20% or more of entity's outstanding common stock shares (in number of days) | D										10
Dividends per common share (in dollars per share) | $ / shares		$ 0.08	$ 0	$ 0	$ 0	$ 0.08	$ 0	$ 0	$ 0		$ 0.08	$ 0.08
Number of shares authorized to be repurchased (in shares) (up to)		10,000,000								10,000,000
Aggregate number of shares repurchased (in shares)										7,600,000
Aggregate cost of shares repurchased | $										$ 49.8