Business Segments, Concentration of Business, and Credit Risk and Significant Customers (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Cash and cash equivalents	$ 64,591	$ 110,247	$ 228,571	$ 263,606
Consolidated total assets	917,443	1,068,064
Amount of loss or lack of access to cash in operating accounts	0
Amount of loss or lack of access to invested cash and cash equivalents	0
Reportable segments
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Consolidated total assets	690,883	816,807
Unallocated to Segments
Reconciliations of total assets from reportable segments to the condensed consolidated balance sheets
Cash and cash equivalents	64,591	110,247
Unallocated deferred tax assets	30,079	30,662
Other unallocated corporate assets	$ 131,890	$ 110,348