Summary of Significant Accounting Policies (New Accounting Pronouncements) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating, selling, administrative and general expenses									$ 355,513	$ 337,191	$ 339,059
Operating income	$ 48,086	$ 66,018	$ 61,861	$ 48,084	$ 48,204	$ 59,723	$ 74,300	$ 53,421	224,049	235,648	234,505
Other, net									10,333	5,426	4,237
Income before provision for income taxes									79,559	89,168	126,429
(Increase) decrease in restricted assets									526	2,250	410
Net cash used in investing activities									43,463	(35,962)	(10,313)
Net (decrease) increase in cash, cash equivalents and restricted cash									280,792	(87,641)	143,391
Cash, cash equivalents and restricted cash, beginning of year				310,937				398,578	310,937	398,578	255,187
Cash and cash equivalents and restricted cash, end of year	$ 591,729				310,937				591,729	310,937	398,578
Impact of adoption of new accounting standards					8,838					8,838			$ (4,576)
Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													6,354
Accumulated Other Comprehensive Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													(6,036)
Accounting Standards Update 2016-01
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													(8,838)
Accounting Standards Update 2016-01 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													(14,874)
Accounting Standards Update 2016-01 | Accumulated Other Comprehensive Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													(6,036)
Real Estate | Accounting Standards Update 2014-09 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													13,415
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating, selling, administrative and general expenses										339,151	340,567
Operating income										233,688	232,997
Other, net										7,386	5,745
Income before provision for income taxes										89,168	126,429
(Increase) decrease in restricted assets										(2,286)	10,181
Net cash used in investing activities										(40,498)	(542)
Net (decrease) increase in cash, cash equivalents and restricted cash										(92,177)	153,162
Cash, cash equivalents and restricted cash, beginning of year				301,353				393,530	301,353	393,530	240,368
Cash and cash equivalents and restricted cash, end of year					301,353					301,353	393,530
As Previously Reported | Real Estate | Accounting Standards Update 2014-09 | Accumulated Deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards													$ (21,695)
Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other, net										7,022	4,732
Adjustment | Accounting Standards Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
(Increase) decrease in restricted assets										4,536	(9,771)
Net cash used in investing activities										4,536	(9,771)
Net (decrease) increase in cash, cash equivalents and restricted cash										4,536	(9,771)
Cash, cash equivalents and restricted cash, beginning of year				$ 9,584				$ 5,048	$ 9,584	5,048	14,819
Cash and cash equivalents and restricted cash, end of year					$ 9,584					9,584	5,048
Adjustment | Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating, selling, administrative and general expenses										(1,960)	(1,508)
Operating income										1,960	1,508
Other, net										(1,960)	(1,508)
Income before provision for income taxes										$ 0	$ 0
Minimum | Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards												$ 130,000
Maximum | Forecast | Accounting Standards Update 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Impact of adoption of new accounting standards												$ 160,000