Reconciliation of Total Segment Assets to Total Assets (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Segment Reporting, Asset Reconciling Item [Line Items]
Total segment assets	$ 2,944,744	$ 2,136,168	$ 2,195,397
Other assets	34,343	39,850
Total assets	$ 2,979,087	$ 2,176,018