Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Cash Flows [Abstract]
Net income	$ 147,874	$ 151,453	$ 121,729
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	298,664	305,216	318,783
Amortization of deferred financing costs	19,435	18,508	14,878
Amortization of lease premiums, discounts and incentives	11,714	10,353	10,664
Deferred income taxes	(8,948)	6,156	(6,889)
Non-cash share-based payment expense	13,148	7,901	5,537
Cash flow hedges reclassified into earnings	2,202	9,662	24,023
Security deposits and maintenance payments included in earnings	(17,947)	(23,123)	(35,843)
Gain on the sale of flight equipment	(55,167)	(39,126)	(58,017)
Impairment of aircraft	80,430	28,585	119,835
Other	1,476	(6,867)	(896)
Changes on certain assets and liabilities:
Accounts receivable	(6,734)	832	(5,406)
Other assets	(7,655)	(1,089)	(5,033)
Accounts payable, accrued expenses and other liabilities	13,857	(4,014)	7,255
Lease rentals received in advance	(1,478)	3,645	15,665
Net Cash and Restricted Cash Provided by (Used in) Operating Activities	490,871	468,092	526,285
Cash flows from investing activities:
Acquisition and improvement of flight equipment	(1,038,343)	(1,331,059)	(1,320,669)
Proceeds from sale of flight equipment	833,576	755,898	562,518
Net investment in finance and sales-type leases	(331,721)	(78,892)	(91,648)
Proceeds from Collection of Finance Receivables	32,184	19,413	9,559
Aircraft purchase deposits and progress payments, net of returned deposits and aircraft sales deposits	(7,681)	(9,628)	(6,812)
Unconsolidated equity method investment and associated costs	0	(18,048)	0
Other	(5,122)	(839)	(610)
Net cash and restricted cash used in investing activities	(517,107)	(663,155)	(847,662)
Cash flows from financing activities:
Repurchase of shares	(4,862)	(37,337)	(20,881)
Proceeds from secured and unsecured debt financings	675,000	1,054,250	975,000
Repayments of secured and unsecured debt financings	(878,534)	(588,778)	(681,393)
Deferred financing costs	(8,540)	(18,890)	(11,881)
Restricted secured liquidity facility collateral	0	65,000	0
Liquidity facility	0	(65,000)	0
Security deposits and maintenance payments received	192,830	171,672	152,391
Security deposits and maintenance payments returned	(141,185)	(51,658)	(33,398)
Dividends paid	(83,433)	(77,137)	(72,960)
Other	0	(2,283)	0
Net cash and restricted cash (used in) provided by financing activities	(248,724)	449,839	306,878
Net (decrease) increase in cash and restricted cash	(274,960)	254,776	(14,499)
Cash and restricted cash at beginning of year	508,817	254,041	268,540
Cash and restricted cash at end of year	233,857	508,817	254,041
Supplemental disclosures of cash flow information:
Cash paid during the year for interest	228,125	224,705	195,162
Cash paid during the year for income taxes	4,576	16,693	12,716
Supplemental disclosures of non-cash investing activities:
Advance lease rentals, security deposits, maintenance payments, other liabilities and other assets settled in sale of flight equipment	132,585	75,335	93,601
Advance lease rentals, security deposits and maintenance payments assumed in asset acquisitions	149,100	202,808	13,307
Transfers from Flight equipment held for lease to Net investment in finance and sales-type leases and Other assets	$ 154,213	$ 142,950	$ 40,327