Consolidated Balance Sheets (Parenthetical) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Allowances	$ 48,138,000	$ 49,364,000
Series A preferred shares, par value (in usd 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	$ 203,067,000
Preferred shares par value (in usd per share)	$ 0.001	$ 0.001
Preferred stock authorized (shares)	4,000,000	4,000,000
Preferred stock outstanding (shares)	0	0
Common shares par value (in usd per share)	$ 0.001	$ 0.001
Common shares issued (shares)	93,900,000	93,100,000
Common shares outstanding (shares)	73,600,000	72,900,000
Treasury stock (shares)	20,300,000	20,200,000