Reconciliation between Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Earnings Per Share Disclosure [Line Items]
Net income for basic and diluted earnings per share	$ 36,562	[1],[2]	$ 398,958	[1],[2]	$ 93,491	[1],[2]	$ 78,410	[1],[2]	$ 31,900	[1],[2]	$ 350,179	[1],[2]	$ 53,731	[1],[2]	$ 79,843	[1],[2]	$ 607,421	$ 515,653	$ 152,485
Weighted-average common shares outstanding																	216,983	215,026	213,809
Dilutive effect of stock options and restricted stock awards																	2,246	2,685	1,486
Diluted weighted-average shares outstanding																	219,229	217,711	215,295
Basic earnings per share:
Net income	$ 0.17	[1]	$ 1.84	[1]	$ 0.43	[1]	$ 0.36	[1]	$ 0.15	[1]	$ 1.63	[1]	$ 0.25	[1]	$ 0.37	[1]	$ 2.80	$ 2.40	$ 0.71
Diluted earnings per share:
Net income	$ 0.17	[1]	$ 1.82	[1]	$ 0.43	[1]	$ 0.36	[1]	$ 0.15	[1]	$ 1.61	[1]	$ 0.25	[1]	$ 0.37	[1]	$ 2.77	$ 2.37	$ 0.71

[1] Amounts for 2010 and amounts for the first quarter of 2011 include a revision for the correction of an error in the manner in which we were amortizing certain guarantee fees. Refer to the tables below which present the effects of the revision on the Company's Consolidated Statements of Operations for these respective periods.

[2] The first quarter of 2010 included a one-time gain of approximately $85.6 million, net of costs and payments to insurers, related to the settlement of our case against Rolls Royce.