Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Cash Flows [Abstract]
Net income	$ 31,112	$ 50,203	$ 65,922	$ 107,750
Adjustments to reconcile net income to net cash and restricted cash provided by operating activities:
Depreciation	89,578	76,181	174,313	151,183
Amortization of deferred financing costs			6,958	7,042
Amortization of lease premiums, discounts and incentives	5,345	3,534	11,056	6,662
Deferred income taxes			7,957	3,126
Non-cash share-based payment expense	3,177	3,076	5,903	5,454
Cash flow hedges reclassified into earnings	0	294	184	595
Proceeds from Collection of Finance Receivables			10,971	13,127
Security deposits and maintenance payments included in earnings			(24,162)	(554)
Gain on sale of flight equipment	(346)	(19,864)	(12,348)	(25,632)
Impairment of flight equipment	7,404	0	7,404	0
Other			209	(7,491)
Changes in certain assets and liabilities:
Accounts receivable			(7,899)	(7,315)
Other assets			3,582	(3,086)
Accounts payable, accrued expenses and other liabilities			(11,619)	(14,799)
Lease rentals received in advance			7,181	16,908
Net cash and restricted cash provided by operating activities			245,612	252,970
Cash flows from investing activities:
Acquisition and improvement of flight equipment			(660,723)	(365,505)
Proceeds from sale of flight equipment			56,924	178,185
Net investment in direct financing and sales-type leases			0	(16,256)
Aircraft purchase deposits and progress payments, net of returned deposits and aircraft sales deposits			18,054	(3,965)
Other			2,241	2,956
Net cash and restricted cash used in investing activities			(591,055)	(204,585)
Cash flows from financing activities:
Repurchase of shares			(14,288)	(14,987)
Proceeds from secured and unsecured debt financings			1,841,848	0
Repayments of secured and unsecured debt financings			(1,105,353)	(128,342)
Deferred financing costs			(12,165)	(1,615)
Security deposits and maintenance payments received			92,514	108,653
Security deposits and maintenance payments returned			(64,788)	(38,718)
Dividends paid			(45,054)	(43,993)
Net cash and restricted cash provided by (used in) financing activities			692,714	(119,002)
Net decrease in cash and restricted cash:			347,271	(70,617)
Cash and restricted cash at beginning of period			167,853	233,857
Cash and restricted cash at end of period	515,124	163,240	515,124	163,240
Cash and cash equivalents	500,373	142,360	500,373	142,360
Restricted cash and cash equivalents	$ 14,751	$ 20,880	14,751	20,880
Supplemental disclosures of non-cash investing activities:
Payments to Acquire Interest in Subsidiaries and Affiliates			$ 7,551	$ 0