Contingencies - Components of Recorded Liability Related to Claims and Contingencies (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Dec. 31, 2011
Schedule of Claims and Contingencies [Line Items]
Total	$ 38,648	$ 126,978	$ 38,734	$ 36,028
Other current liabilities	35,573	85,655	14,229
Other liabilities	3,075	41,323	24,505
Total	38,648	126,978	38,734	36,028
PEAKS Guarantee [Member]
Schedule of Claims and Contingencies [Line Items]
Total	0	47,500	0
Total	0	47,500	0
2009 RSA [Member]
Schedule of Claims and Contingencies [Line Items]
Total	31,832	28,232	9,511
Total	31,832	28,232	9,511
2007 RSA [Member]
Schedule of Claims and Contingencies [Line Items]
Total	0	46,000	24,250
Total	0	46,000	24,250
Other claims and contingencies [Member]
Schedule of Claims and Contingencies [Line Items]
Total	6,816	5,246	4,973
Total	$ 6,816	$ 5,246	$ 4,973