Capital Stock - Shares Released from Grantor Stock (Details) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Schedule Of Employee Benefit Plans [Line Items]
Total shares released from the GST	291
Employee restricted stock units vested
Schedule Of Employee Benefit Plans [Line Items]
Total shares released from the GST	205
Employee stock plan purchases
Schedule Of Employee Benefit Plans [Line Items]
Total shares released from the GST	86