Income Taxes - Effective Tax Rate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the Federal statutory income tax rate to the effective income tax rate, Amount
Federal statutory income tax expense	$ 130,140	$ 120,129	$ 120,485
State and local taxes, net of federal income tax benefit	13,884	12,804	12,739
Nontaxable income	(4,628)	(3,570)	(4,972)
Other	2,255	84	(680)
Total provision for income taxes	$ 141,651	$ 129,447	$ 127,572
Reconciliation of the Federal statutory income tax rate to the effective income tax rate, Percent
Federal statutory income tax rate, Percent	35.00%	35.00%	35.00%
State and local taxes, net of federal income tax benefit (as a percent)	3.73%	3.73%	3.70%
Nontaxable income (as a percent)	(1.24%)	(1.04%)	(1.44%)
Other (as a percent)	0.61%	0.02%	(0.20%)
Effective Income Tax Rate Reconciliation, Percent, Total	38.10%	37.71%	37.06%