Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($)	Sep. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowances	$ 20,508,000	$ 31,389,000
Accumulated depreciation	$ 81,043,000	$ 91,806,000
Series A preferred shares, par value (in dollars per share)	$ 0.001	$ 0.001
Series A preferred shares authorized (shares)	1,000,000	1,000,000
Series A preferred shares outstanding (shares)	200,000	200,000
Series A preferred shares, liquidation preference	$ 203,000,000	$ 203,000,000
Preferred shares, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred shares authorized (shares)	4,000,000	4,000,000
Preferred shares outstanding (shares)	0	0
Common shares, par value (in dollars per share)	$ 0.001	$ 0.001
Common Stock, Shares Authorized	250,000,000	250,000,000
Common shares issued (shares)	96,000,000	94,800,000
Common shares outstanding (shares)	67,600,000	68,800,000
Treasury stock (shares)	28,400,000	26,000,000