Shareholders' Equity - Shelf Registration Statements on Form S-4 and Stock Purchase Rights (Details)	May. 02, 2008 $ / shares	Sep. 21, 1998 shares	Dec. 31, 2015 registration_statement $ / shares shares	Dec. 31, 2014 $ / shares
Shelf Registration Statements on Form S-4
Number of effective registration statements (registration statement) | registration_statement			2
Remaining shares available for issuance under registration statement (shares) | shares			13,469,000
Stock Purchase Rights
Par value (in dollars per share)			$ 0.01	$ 0.01
Preferred stock purchase right
Stock Purchase Rights
Preferred stock purchase right issued as dividend | shares		1
Amended Rights Agreement
Stock Purchase Rights
Number of rights held by the shareholders for each share of common stock	$ 1
Minimum percentage of beneficial ownership interest in the entity's common stock to be acquired by a party for the Rights to be exercisable	15.00%
Minimum percentage of consolidated assets, cash flow or earning power to be sold for the Rights to be exercisable	50.00%
Amended Rights Agreement | Series A Junior Participating Preferred Stock
Stock Purchase Rights
Fraction of a share of Series A Junior Participating Preferred Stock that could be purchased for each Right	$ 0.001
Par value (in dollars per share)	0.01
Purchase price per one one-thousandth of a share of Series A Junior Participating Preferred Stock (in dollars per share)	37
Redemption price (in dollars per share)	$ 0.001