Income Taxes (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Income Tax Provision [Abstract]
Current Income Tax Expense (Benefit)									$ 21,459,000	$ 48,384,000	$ (3,908,000)
Deferred Income Tax Expense (Benefit)									95,742,000	62,909,000	22,952,000
Income Tax Expense (Benefit)	33,852,000	33,270,000	11,822,000	38,257,000	31,723,000	23,343,000	27,403,000	28,824,000	117,201,000	111,293,000	19,044,000
Tax Benefit from Stock Options Exercised									2,500,000	5,000,000	(1,200,000)
Effective Income Tax Rate, Continuing Operations, Tax Rate Reconciliation [Abstract]
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate									109,226,000	95,489,000	11,728,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate									35.00%	35.00%	35.00%
income tax reconciliation, state, local and foreign income taxes, net of federal income tax benefit									10,508,000	9,415,000	4,133,000
Effective Income Tax Reconciliation, state, local and foreign income taxes, net of federal income tax benefit									3.40%	3.50%	12.30%
Income tax reconciliation, reduction for tax positions settled, net of federal income tax benefit									80,000	(1,676,000)	(12,324,000)
Effective income tax rate reconciliation, reduction for tax positions settled, net of federal income tax benefit									0.00%	(0.60%)	(36.80%)
Income Tax Reconciliation, Tax Settlements									0	7,000,000	13,746,000
Effective Income Tax Rate Reconciliation, Tax Settlements									0.00%	2.60%	41.00%
Income Tax Reconciliation, Other Adjustments									(2,613,000)	1,065,000	1,761,000
Effective Income Tax Rate Reconciliation, Other Adjustments									(0.80%)	0.30%	5.30%
Effective Income Tax Rate, Continuing Operations									37.60%	40.80%	56.80%
Income Taxes Paid									44,100,000	6,400,000	23,600,000
Deferred Tax Assets, Valuation Allowance	21,037,000				20,502,000				21,037,000	20,502,000
Unrecognized Tax Benefits	$ 14,216,000				$ 17,091,000				$ 14,216,000	$ 17,091,000	$ 18,034,000	$ 27,700,000