Stock-Based Compensation and Other Employee Benefit Plans (Schedule of Non-Cash Stock-Based Compensation Expense and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Non-cash stock-based compensation expense				$ 6,571	$ 7,166
Income Tax Effects:
Income tax effect of non-cash stock-based compensation		$ 1,000	$ 1,300	1,800	2,500
Excess tax benefit from non-cash stock-based compensation	[1]	200	0	200	100
Tax benefits (deficiencies), net		(35,782)	(55,434)	(46,908)	(82,792)
Share-Based Compensation [Member]
Income Tax Effects:
Tax benefits (deficiencies), net				200	(100)
General and Administrative Expenses [Member]
Stock-Based Compensation and Other Employee Benefit Plans [Line Items]
Non-cash stock-based compensation expense		$ 3,400	$ 3,400	$ 6,600	$ 7,200

[1] Excess tax benefits represent cash flows from tax deductions in excess of the tax effect of compensation expense associated with share-based payment arrangements. For the six month period ended June 30, 2018, tax benefits, net of tax deficiencies, related to the vesting of share-based payment awards were $0.2 million, and for the six month period ended June 30, 2017, the Company recognized a tax deficiency, net of tax benefits, of $0.1 million.