Income Taxes (Income Tax Expense) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal									$ 96,364	$ 73,194	$ 97,575
State and local									11,061	5,429	10,970
Total current									107,425	78,623	108,545
Deferred:
Federal									39,568	12,542	(7,279)
State and local									(48,642)	5,158	(8,234)
Total deferred									(9,074)	17,700	(15,513)
Total:
Total federal									135,932	85,736	90,296
Total state and local									(37,581)	10,587	2,736
Income tax expense	$ 17,029	$ 30,281	$ 29,090	$ 21,951	$ 23,845	$ 24,445	$ 24,599	$ 23,434	$ 98,351	$ 96,323	$ 93,032