Seaspan (SESCF) 20-F 10 Mar 15 2014 FY Annual report (foreign) Financial data

Document_and_Entity_Informatio

Document and Entity Information	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Document Information [Line Items]
Document Type	20-F
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Trading Symbol	SSW
Entity Registrant Name	Seaspan CORP
Entity Central Index Key	1332639
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Preferred Stock, Shares Outstanding	24,170,531	18,970,531
Class A Common Shares [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding	96,662,928
Series C Preferred Shares [Member]
Document Information [Line Items]
Entity Preferred Stock, Shares Outstanding	13,665,531
Series D Preferred Shares [Member]
Document Information [Line Items]
Entity Preferred Stock, Shares Outstanding	5,105,000
Series E Preferred Shares [Member]
Document Information [Line Items]
Entity Preferred Stock, Shares Outstanding	5,400,000

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$201,755	$476,380
Short-term investments	1,212	11,675
Accounts receivable (note 4)	23,742	14,149
Loans to affiliate (note 4)	237,908	54,068
Prepaid expenses	31,139	22,671
Gross investment in lease (note 5)	21,170	21,170
Total current assets	516,926	600,113
Vessels (note 6)	5,095,723	4,992,271
Deferred charges (note 7)	64,655	53,971
Gross investment in lease (note 5)	37,783	58,953
Goodwill	75,321	75,321
Other assets (note 8)	67,308	106,944
Fair value of financial instruments (note 18(d))	37,677	60,188
Total assets	5,895,393	5,947,761
Current liabilities:
Accounts payable and accrued liabilities (note 15(a))	65,208	65,634
Current portion of deferred revenue (note 9)	27,671	27,683
Current portion of long-term debt (note 10)	298,010	388,159
Current portion of other long-term liabilities (note 11)	18,543	38,930
Fair value of financial instruments (note 18(d))	7,505
Total current liabilities	416,937	520,406
Deferred revenue (note 9)	7,343	4,143
Long-term debt (note 10)	3,084,409	2,853,459
Other long-term liabilities (note 11)	253,542	572,673
Fair value of financial instruments (note 18(d))	387,938	425,375
Share capital (note 12):
Common and Preferred Shares	1,209	882
Treasury shares	-379	-379
Additional paid in capital	2,238,872	2,023,622
Deficit	-459,161	-411,792
Accumulated other comprehensive loss	-35,317	-40,628
Total Shareholders' equity	1,745,224	1,571,705
Total liabilities and shareholders' equity	5,895,393	5,947,761
Commitments and contingent obligations (note 16)
Subsequent events (note 19)	$0	$0

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Preferred shares, par value	$0.01	$0.01
Preferred shares, authorized	150,000,000	65,000,000
Preferred shares, issued	24,170,531	18,970,531
Preferred shares, outstanding	24,170,531	18,970,531
Class A Common Shares [Member]
Common shares, par value	$0.01	$0.01
Common shares, authorized	200,000,000	200,000,000
Common shares, issued	96,662,928	69,208,888
Common shares, outstanding	96,662,928	69,208,888

Consolidated_Statements_of_Ope

Consolidated Statements of Operations (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenue	$717,170	$677,090	$660,794
Operating expenses:
Ship operating (note 4)	166,097	150,105	138,655
Depreciation and amortization	181,527	172,459	165,541
General and administrative	30,462	34,783	24,617
Operating leases (note 11(c))	9,544	4,388	3,145
Gain on vessel (notes 6)			-9,773
Total operating expenses	387,630	361,735	322,185
Operating earnings	329,540	315,355	338,609
Other expenses (income):
Interest expense	88,159	60,496	71,996
Interest income	-10,653	-2,045	-1,190
Undrawn credit facility fees	3,109	2,725	1,516
Amortization of deferred charges (note 7)	10,342	9,477	8,574
Refinancing expenses and recoveries (note 7)	70	4,038
Change in fair value of financial instruments (note 18(b))	105,694	-60,504	135,998
Equity (income) loss on investment (note 8(a))	-256	670	259
Other expenses	1,828	1,470	151
Total Other expenses (income)	198,293	16,327	217,304
Net earnings	$131,247	$299,028	$121,305
Earnings per share (note 13):
Class A common share, basic	$0.80	$3.36	$0.84
Class A common share, diluted	$0.79	$2.93	$0.81

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (Loss) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net earnings	$131,247	$299,028	$121,305
Other comprehensive income:
Amounts reclassified to net earnings during the period relating to cash flow hedging instruments (note 18 (b))	5,311	6,212	9,146
Comprehensive income	$136,558	$305,240	$130,451

Consolidated_Statements_of_Sha

Consolidated Statements of Shareholders' Equity (USD $)	Total	Series D Preferred Shares [Member]	Class A Common Shares [Member]	Series C Preferred Shares [Member]	Series E Preferred Shares [Member]	Series C, Series D, and Series E Preferred Share [Member]	Series C and D Preferred Share [Member]	Class A Common Shares [Member]	Class C common Shares [Member]	Series A Preferred Shares [Member]	Series C Preferred Shares [Member]	Series D Preferred Shares [Member]	Series E Preferred Shares [Member]	Common Shares [Member]	Common Shares [Member]	Preferred Shares [Member]	Preferred Shares [Member]	Preferred Shares [Member]	Treasury Shares [Member]	Treasury Shares [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member]	Deficit [Member]	Deficit [Member]	Deficit [Member]	Deficit [Member]	Deficit [Member]	Accumulated Other Comprehensive Loss [Member]
	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)	USD ($)							USD ($)	Class A Common Shares [Member]	USD ($)	Series D Preferred Shares [Member]	Series E Preferred Shares [Member]	USD ($)	Class A Common Shares [Member]	USD ($)	Series D Preferred Shares [Member]	Class A Common Shares [Member]	Series C Preferred Shares [Member]	Series E Preferred Shares [Member]	USD ($)	Class A Common Shares [Member]	Series C Preferred Shares [Member]	Series C, Series D, and Series E Preferred Share [Member]	Series C and D Preferred Share [Member]	USD ($)
															USD ($)		USD ($)	USD ($)		USD ($)		USD ($)	USD ($)	USD ($)	USD ($)		USD ($)	USD ($)	USD ($)	USD ($)
Balance at Dec. 31, 2011	$1,183,425,000													$696,000		$142,000					$1,860,979,000					($622,406,000)					($55,986,000)
Balance, shares at Dec. 31, 2011								69,620,060	100	200,000	14,000,000
Net earnings	121,305,000																									121,305,000
Other comprehensive income	9,146,000																														9,146,000
Shares issued and retired on acquisition (note 3)	83,275,000													42,000							83,233,000
Shares issued and retired on acquisition (note 3), shares								4,220,728	-100
Shares issued, value		77,625,000															31,000					77,594,000
Dividends on preferred shares				-33,250,000																								-33,250,000
Shares issued, shares												3,105,000
Dividends on class A common shares			-58,940,000																								-58,940,000
Amortization of Series C issuance costs																								862,000				-862,000
Fees and expenses in connection with issuance of common and preferred shares	-2,929,000																				-2,929,000
Shares repurchased, including related expenses, shares			-148,101					-11,448,101
Shares issued through dividend reinvestment program (note 12(a))	7,168,000													5,000									7,163,000
Shares issued through dividend reinvestment program (note 12(a)), shares								474,249
Other share-based compensation			839,000																				839,000
Share-based compensation expense (note 14):
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units	4,028,000													3,000									4,025,000
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units, shares								194,714
Treasury shares, value	-313,000													-1,000						-312,000
Treasury shares								-19,433
Shares repurchased, including related expenses	-172,812,000		-2,203,000											-114,000									-172,698,000
Balance at Dec. 31, 2012	1,218,567,000													631,000		173,000			-312,000		1,859,068,000					-594,153,000					-46,840,000
Balance, shares at Dec. 31, 2012								63,042,217		200,000	14,000,000	3,105,000
Net earnings	299,028,000																									299,028,000
Other comprehensive income	6,212,000																														6,212,000
Shares issued, value		50,000,000	77,000,000												35,000		20,000					49,980,000	76,965,000
Dividends on preferred shares							-38,493,000																							-38,493,000
Shares issued, shares								3,500,000				2,000,000
Dividends on class A common shares			-76,340,000																								-76,340,000
Amortization of Series C issuance costs																								1,174,000				-1,174,000
Fees and expenses in connection with issuance of common and preferred shares	-5,959,000																				-5,959,000
Shares repurchased, including related expenses, shares											-334,469
Shares issued through dividend reinvestment program (note 12(a))	31,961,000													16,000									31,945,000
Shares issued through dividend reinvestment program (note 12(a)), shares								1,561,838
Other share-based compensation	4,742,000													2,000									4,740,000
Share-based compensation expense (note 14):
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units	14,004,000																						14,004,000
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units, shares								79,088
Other share-based compensation, shares								206,200
Fleet growth payments														8,000									-8,000
Fleet growth payments (note 3),shares								820,697
Treasury shares, value	-67,000																		-67,000
Treasury shares								-1,152
Shares repurchased, including related expenses	-8,950,000															-3,000								-8,287,000				-660,000
Balance at Dec. 31, 2013	1,571,705,000													692,000		190,000			-379,000		2,023,622,000					-411,792,000					-40,628,000
Balance, shares at Dec. 31, 2013								69,208,888		200,000	13,665,531	5,105,000
Net earnings	131,247,000																									131,247,000
Other comprehensive income	5,311,000																														5,311,000
Conversion of Series A preferred shares (note 12(b))														232,000		-2,000					-230,000
Conversion of Series A preferred shares (note 12(b)),shares								23,177,175		-200,000
Shares issued, value			4,733,000		135,000,000										2,000			54,000					4,731,000		134,946,000
Dividends on preferred shares						-50,443,000																							-50,443,000
Shares issued, shares			206,600					206,600					5,400,000
Dividends on class A common shares			-127,007,000																								-127,007,000
Amortization of Series C issuance costs																								1,166,000				-1,166,000
Fees and expenses in connection with issuance of common and preferred shares	-5,073,000																				-5,073,000
Shares issued through dividend reinvestment program (note 12(a))	64,697,000													31,000									64,666,000
Shares issued through dividend reinvestment program (note 12(a)), shares								3,043,731
Other share-based compensation	7,353,000													3,000									7,350,000
Share-based compensation expense (note 14):
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units	7,701,000													2,000									7,699,000
Restricted class A common shares, phantom share units, stock appreciation rights issued and restricted stock units, shares								214,464
Other share-based compensation, shares								344,438
Fleet growth payments														5,000									-5,000
Fleet growth payments (note 3),shares								468,968
Treasury shares								-1,336
Balance at Dec. 31, 2014	$1,745,224,000													$967,000		$242,000			($379,000)		$2,238,872,000					($459,161,000)					($35,317,000)
Balance, shares at Dec. 31, 2014								96,662,928			13,665,531	5,105,000	5,400,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities:
Net earnings	$131,247	$299,028	$121,305
Items not involving cash:
Depreciation and amortization	181,527	172,459	165,541
Share-based compensation (note 14)	8,301	14,604	4,779
Amortization of deferred charges (note 7)	10,342	9,477	8,574
Amounts reclassified from other comprehensive loss to interest expense	4,259	5,330	8,310
Unrealized change in fair value of financial instruments	-13,064	-187,522	11,215
Gain on vessel			-9,773
Equity (income) loss on investment (note 8(a))	-256	670	259
Refinancing expenses and recoveries (note 7)	-398	2,017
Operating leases (note 11(c))	-1,428
Other	10,614	720
Changes in assets and liabilities:
Accounts receivable	-9,593	-4,577	5,773
Lease receivable	21,170	15,675	14,640
Prepaid expenses	856	-1,769	6,226
Other assets and deferred charges	-9,380	-2,716	-5,846
Accounts payable and accrued liabilities	9,046	6,071	-18,247
Deferred revenue	3,188	-1,188	-2,746
Other long-term liabilities	-3,472	-610	1,173
Cash from operating activities	342,959	327,669	311,183
Financing activities:
Senior unsecured notes issued (note 10(c))	345,000
Preferred shares issued, net of issuance costs (note 12(b))	130,415	47,862	74,700
Common shares issued, net of issuance costs (note 12(a))	4,245	73,179
Draws on credit facilities	507,040	164,000	113,672
Repayment of credit facilities	-872,659	-67,406	-44,569
Repayment of other long-term liabilities (note 11)	-393,382	-39,988	-53,516
Shares repurchased, including related expenses (note 12(b))		-8,950	-172,812
Financing fees (note 7)	-17,405	-23,334	-3,817
Dividends on common shares	-62,310	-44,379	-51,772
Dividends on preferred shares	-50,443	-38,493	-33,250
Proceeds from sale-leaseback of vessels (note 11(c))	330,000
Swaption premium payment			-10,000
Cash from (used in) financing activities	-79,499	62,491	-181,364
Investing activities:
Expenditures for vessels	-371,135	-255,593	-209,599
Short-term investments	10,463	24,425	-35,737
Cash acquired on acquisition of Seaspan Management Services Ltd.			23,911
Restricted cash	60,000	-1,755	-7,100
Loans to affiliate (note 4)	-210,713	-93,700
Repayment from loans to affiliate (note 4)	850	39,633
Other assets	-27,550	-3,724	-1,039
Investment in affiliate (note 8(a))		-4,444
Cash used in investing activities	-538,085	-295,158	-229,564
Increase (decrease) in cash and cash equivalents	-274,625	95,002	-99,745
Cash and cash equivalents, beginning of year	476,380	381,378	481,123
Cash and cash equivalents, end of year	201,755	476,380	381,378
Supplemental cash flow information (note 14(b))	$0	$0	$0

General

General	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
General	1	General:
	Seaspan Corporation (the “Company”) was incorporated on May 3, 2005 in the Marshall Islands and owns and operates containerships pursuant to primarily long-term, fixed-rate time charters to major container liner companies.

Summary_of_significant_account

Summary of significant accounting policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of significant accounting policies	2	Summary of significant accounting policies:
		(a)	Basis of presentation:
	These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and the following accounting policies have been consistently applied in the preparation of the consolidated financial statements.
		(b)	Principles of consolidation:
	The accompanying consolidated financial statements include the accounts of Seaspan Corporation and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated upon consolidation.
	The Company also consolidates any variable interest entities (“VIEs”) of which it is the primary beneficiary. The primary beneficiary is the enterprise that has both the power to make decisions that most significantly affect the economic performance of the VIE and has the right to receive benefits or the obligation to absorb losses that in either case could potentially be significant to the VIE. The impact of the consolidation of these VIEs is described in note 11.
	The Company accounts for its investment in companies in which it has significant influence by the equity method. The Company’s proportionate share of earnings (loss) is included in earnings and added to or deducted from the cost of the investment.
		(c)	Foreign currency translation:
	The functional and reporting currency of the Company is the United States dollar. Transactions involving other currencies are converted into United States dollars using the exchange rates in effect at the time of the transactions. At the balance sheet date, monetary assets and liabilities that are denominated in currencies other than the United States dollar are translated into United States dollars using exchange rates at that date. Exchange gains and losses are included in net earnings.
		(d)	Cash equivalents:
	Cash equivalents include highly liquid securities with terms to maturity of three months or less when acquired.
		(e)	Vessels:
	Except as described below, vessels are recorded at their cost, which consists of the purchase price, acquisition and delivery costs, less accumulated depreciation.
	Vessels purchased from the predecessor upon completion of the Company’s initial public offering in 2005 were initially recorded at the predecessor’s carrying value.
	Vessels under construction include deposits, installment payments, interest, financing costs, construction design, supervision costs, and other pre-delivery costs incurred during the construction period.
	Depreciation is calculated on a straight-line basis over the estimated useful life of each vessel, which is 30 years from the date of completion. The Company calculates depreciation based on the estimated remaining useful life and the expected salvage value of the vessel.
	Vessels that are held for use are evaluated for impairment when events or circumstances indicate that their carrying amounts may not be recoverable from future undiscounted cash flows. Such evaluations include the comparison of current and anticipated operating cash flows, assessment of future operations and other relevant factors. If the carrying amount of the vessel exceeds the estimated net undiscounted future cash flows expected to be generated over the vessel’s remaining useful life, the carrying amount of the vessel is reduced to its estimated fair value.
		(f)	Dry-dock activities:
	Classification rules require that vessels be dry-docked for inspection including planned major maintenance and overhaul activities for ongoing certification. The Company generally dry-docks its vessels once every five years. Dry-docking activities include the inspection, refurbishment and replacement of steel, engine components, electrical, pipes and valves, and other parts of the vessel. The Company has adopted the deferral method of accounting for dry-dock activities whereby costs incurred are deferred and amortized on a straight-line basis over the period until the next scheduled dry-dock activity.
		(g)	Goodwill and intangible assets:
	Goodwill represents the excess of the purchase price of an acquired enterprise over the fair value assigned to assets acquired and liabilities assumed in a business combination. Goodwill is not amortized, but reviewed for impairment annually or more frequently if impairment indicators arise. When goodwill is reviewed for impairment, the Company may elect to assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, including goodwill. Alternatively, the Company may bypass this step and use a fair value approach to identify potential goodwill impairment and, when necessary, measure the amount of impairment. The Company uses a discounted cash flow model to determine the fair value of reporting units, unless there is a readily determinable fair market value.
	Intangible assets with finite lives are amortized over their useful lives. Intangible assets with finite lives are assessed for impairment when and if impairment indicators exist. An impairment loss is recognized if the carrying amount of an intangible asset is not recoverable and its carrying amount exceeds its fair value.
		(h)	Deferred financing fees:
	Deferred financing fees represent the unamortized costs incurred on issuance of the Company’s credit and lease facilities. Amortization of deferred financing fees on leases is provided on the effective interest rate method over the term of the underlying obligation. Amortization of deferred financing fees on credit facilities is provided on the effective interest rate method over the term of the facility based on amounts available under the facilities.
		(i)	Revenue recognition:
	The Company derives its revenues primarily from the charter of its vessels. Each charter agreement is evaluated and classified as an operating or capital lease. For time charters classified as operating leases, revenue for the lease and service components is recognized each day the vessel is on-hire and when collection is reasonably assured.
	For capital leases that are sales-type leases, the difference between the gross investment in lease and the present value of its components, i.e. the minimum lease payments and the estimated residual value, is recorded as unearned lease interest income. The discount rate used in determining the present values is the interest rate implicit in the lease. The present value of the minimum lease payments, computed using the interest rate implicit in the lease, is recorded as the sales price, from which the carrying value of the vessel at the commencement of the lease is deducted in order to determine the profit or loss on sale. Unearned lease interest income is amortized to income over the period of the lease so as to produce a constant periodic rate of return on the net investment in lease.
	Revenue from vessel management is recognized each day the vessel is managed and when collection is reasonably assured.
	Project revenue is recorded on the completed contract basis when the project is substantially complete and the collectability of any outstanding funds is reasonably assured. Funds received from customers prior to substantial completion of the contract are recorded as deferred revenue.
		(j)	Leases:
	Leases, where the Company is the lessee, are classified as either capital leases or operating leases based on an assessment of the terms of the lease.
	For sale-leaseback transactions, the Company, as seller-lessee, would recognize a gain or loss over the term of the lease as an adjustment to the lease expense, unless the loss is required to be recognized immediately by accounting standards. The term of the lease includes the fixed non-cancelable term of the lease plus all renewal periods such that renewal appears reasonably assured.
		(k)	Derivative financial instruments:
	The Company’s hedging policies permit the use of various derivative financial instruments to manage interest rate risk. The Company has entered into interest rate swaps and swaptions to reduce the Company’s exposure to changing interest rates on its credit and lease facilities.
	All of the Company’s derivatives are measured at their fair value at the end of each period. For derivatives not designated as accounting hedges, changes in their fair value are recorded in earnings.
	The Company had previously designated certain of its interest rate swaps as accounting hedges and applied hedge accounting to those instruments. While hedge accounting was applied, the effective portion of the unrealized gains or losses on those designated interest rate swaps was recorded in other comprehensive loss.
	By September 30, 2008, the Company de-designated all of the interest rate swaps it had accounted for as hedges to that date. Subsequent to their de-designation dates, changes in their fair value are recorded in earnings.
	The Company evaluates whether the occurrence of any of the previously hedged interest payments are considered to be remote. When the previously hedged interest payments are not considered remote of occurring, unrealized gains or losses in accumulated other comprehensive income associated with the previously designated interest rate swaps are recognized in earnings when and where the interest payments are recognized. If such interest payments are identified as being remote, the accumulated other comprehensive income balance pertaining to these amounts is reversed through earnings immediately.
		(l)	Fair value measurement:
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e. the “exit price”) in an orderly transaction between market participants at the measurement date. The hierarchy is broken down into three levels based on the observability of inputs as follows:
		•		Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. Valuation adjustments and block discounts are not applied to Level 1 instruments. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of these products does not entail a significant degree of judgment.
		•		Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly.
		•		Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.
		(m)	Share-based compensation:
	The Company has granted restricted shares, phantom share units, stock appreciation rights (“SARs”) and restricted stock units to certain of its officers, members of management and directors as compensation. Compensation cost is measured at their grant date fair values. Under this method, restricted shares, phantom share units and restricted stock units are measured based on the quoted market price of the Company’s Class A common shares at date of the grant, and SARs are measured at fair value using the Monte Carlo model. The fair value of each grant is recognized straight-line over the requisite service period.
		(n)	Earnings per share:
	The Company had multiple classes of common shares with different participation rights and applied the two-class method to compute basic earnings per share (“EPS”) until the acquisition and cancellation of those shares in January 2012.
	The treasury stock method is used to compute the dilutive effect of the Company’s share-based compensation awards. Under this method, the incremental number of shares used in computing diluted EPS is the difference between the number of shares assumed issued and purchased using assumed proceeds.
	The if-converted method was used to compute the dilutive effect of the Company’s Series A preferred shares until January 30, 2014, the date the Company’s outstanding 200,000 Series A preferred shares automatically converted into Class A common shares. Under the if-converted method, dividends applicable to the Series A preferred shares were added back to earnings attributable to common shareholders, and the Series A preferred shares and paid-in kind dividends were assumed to have been converted at the share price applicable at the end of the period. The if-converted method was applied to the computation of diluted EPS only if the effect was dilutive.
	The dividends applicable to the Series C, D and E preferred shares reduce the earnings available to common shareholders, even if not declared, since the dividends are cumulative.
		(o)	Use of estimates:
	The preparation of consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the balance sheet dates and the reported amounts of revenue and expenses during the reporting fiscal periods. Areas where accounting judgments and estimates are significant to the Company include the assessment of the vessel useful lives, expected salvage values and the recoverability of the carrying value of vessels which are subject to future market events, carrying value of goodwill and the fair value of interest rate derivative financial instruments and share-based awards. Actual results could differ from those estimates.
		(p)	Comparative information:
	Certain information has been reclassified to conform with the financial statement presentation adopted for the current year.
		(q)	Recent accounting pronouncements:
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update, or ASU 2014-09, Revenue from Contracts with Customers, that introduced a new five-step revenue recognition model to be used to determine how an entity should recognize revenue related to the transfer of goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services.
	This ASU also requires disclosures sufficient to enable users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers, including qualitative and quantitative disclosures about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. This standard is effective for fiscal years beginning after December 15, 2016, including interim periods within that reporting period. We are currently evaluating the new guidance to determine the impact it will have on our consolidated financial statements.

Acquisition_of_Seaspan_Managem

Acquisition of Seaspan Management Services Limited	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Acquisition of Seaspan Management Services Limited	3	Acquisition of Seaspan Management Services Limited:
	On January 27, 2012, the Company acquired 100 percent of Seaspan Management Services Limited (the “Manager”), an affiliated privately owned company that has provided technical, administrative and strategic services to the Company. The Company’s acquisition of the Manager has increased its control over access to the fixed-rate services that the Manager provides to the Company on a long-term basis, and reduced certain conflicts between the Company and its directors who have interests in the Manager.
	The aggregate purchase price was $106,518,000, including:
	4,220,728 of the Company’s Class A common shares		$	66,899
	Contingent consideration			18,437
	Settlement of intercompany balances			20,022
	Stock based compensation			1,160
	Aggregate purchase price		$	106,518
	Under the Share Purchase Agreement, $7,500,000 or 586,212 shares of Class A common shares were deposited in escrow for settlement of potential indemnifiable damages. The escrowed shares were released on January 30, 2013, the end of the escrow period.
	The value of the Company’s Class A common shares issued was determined based on the closing market price of those common shares on January 26, 2012.
	The contingent consideration arrangement requires the Company to pay the former owners of the Manager additional consideration of 39,081 of the Company’s Class A common shares for each of certain containerships ordered or acquired by the Company, Greater China Intermodal Investments LLC (“GCI”) or Blue Water Commerce, LLC (collectively, the “Contingency Parties”) after December 12, 2011 and prior to August 15, 2014 and which are to be managed by the Manager or the Company. The fair value of the contingent consideration is based on the estimated containership orders and acquisitions of each of the Contingency Parties prior to August 15, 2014.
	For the year ended December 31, 2014, total shares issued related to this contingent consideration arrangement were 195,404 (2013—820,697).
	For the year ended December 31, 2014, no acquisition-related costs (2013—nil; 2012—$1,184,000) have been included in general and administrative expense in the Company’s consolidated statements of operations.

Related_party_transactions

Related party transactions	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Related party transactions	4	Related party transactions:
		(a)	At December 31, 2014, the Company had $237,908,000 (2013—$54,068,000) due from GCI recorded as loans to affiliate. This amount includes the following:
		•		The Company had $219,841,000 (2013—$53,309,000) due from GCI for payments made in connection with vessels that GCI will acquire pursuant to a right of first refusal. These loans, which are due on demand, bear interest at rates ranging from 5% to 7% per annum.
		•		In August 2014, GCI issued a promissory note to the Company for $25,000,000 which bears interest at 7% per annum. In September 2014, the Company entered into an agreement with GCI to reallocate two of the Company’s vessels for two of the vessels that GCI had previously selected under the right of first refusal, resulting in a payable to GCI of which $9,780,000 which was applied against the promissory note. In December 2014, the Company made a capital contribution of $6,667,000 which was applied against the promissory note (notes 8(a) and 15(b)).
		•		The interest receivable on these amounts is $9,514,000 (2013—$759,000).
	The Company also had $8,195,000 (2013—$2,084,000) due from GCI included in accounts receivable and $6,788,000 (2013—$611,000) due to GCI included in accounts payable and accrued liabilities.
	The Company also had $1,454,000 (2013—$1,614,000) due from other related parties included in accounts receivable.
		(b)	The Company incurred the following income or expenses with related parties:
			2014		2013		2012
	Fees paid:
	Arrangement fees		$	4,520	$	6,631	$	1,790
	Transaction fees			7,323		3,532		123
	Reimbursed expenses			237		72		—
	Income received:
	Interest income			9,888		1,150		—
	Management fees			913		69		—
	The income or expenses with related parties relate to amounts paid to or received from individuals or entities that are associated with the Company’s directors or officers and these transactions are governed by pre-arranged contracts.
	Arrangement fees are paid to related parties in connection with services associated with debt or lease financing and are generally recorded as deferred financing fees and amortized over the term of the related debt or lease.
	Transaction fees are paid to related parties in connection with services they provided related to newbuild contracts, purchase or sale contracts and are capitalized to vessels.
	Arrangement fees and transaction fees are paid either in cash or, at the Company’s discretion, a combination of cash and up to 50% in the Company’s common shares (note 14(iv)).
	Interest income is earned on loans to affiliate.
	Management fees are earned from GCI for the management of GCI’s vessels and are included in revenue.
		(c)	Prior to the acquisition of the Manager on January 27, 2012, the Company had management agreements with the Manager for the provision of certain services and incurred costs of $9,700,000 (technical services, including $421,000 relating to dry-dock activities) and $410,000 (other services) for the 26 days prior to acquisition in 2012.

Gross_investment_in_lease

Gross investment in lease	12 Months Ended
	Dec. 31, 2014
Leases [Abstract]
Gross investment in lease	5	Gross investment in lease:
			2014			2013
	Gross investment in lease		$	58,953		$	80,123
	Current portion			(21,170	)		(21,170	)
			$	37,783		$	58,953
	In 2011, the Company entered into five-year bareboat charters for four of its vessels whereby the lessee will purchase the vessels for $5,000,000 each at the end of each lease term. Each lease is considered a sales type lease and was accounted for as a disposition of the vessel upon its delivery in 2011. The gross investment is offset by deferred interest on lease receivable.

Vessels

Vessels	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Vessels	6	Vessels:
	December 31, 2014		Cost		Accumulated		Net book
					depreciation		value
	Vessels		$	5,708,685	$	894,964	$	4,813,721
	Vessels under construction			282,002		—		282,002
	Vessels		$	5,990,687	$	894,964	$	5,095,723
	December 31, 2013		Cost		Accumulated		Net book
					depreciation		value
	Vessels		$	5,391,713	$	720,814	$	4,670,899
	Vessels under construction			321,372		—		321,372
	Vessels		$	5,713,085	$	720,814	$	4,992,271
	During the year ended December 31, 2014, the Company capitalized interest costs of $8,184,000 (2013—$2,873,000; 2012—$2,983,000) to vessels under construction.
	On June 1, 2012, the $53,000,000 term loan credit facility with a U.S. bank matured upon expiration of the UASC Madinah time charter. On June 27, 2012, the Company sold the UASC Madinah to that U.S. bank for $52,104,000, the amount outstanding under the term loan resulting in a gain on vessel of $9,773,000. The Company is leasing the vessel back for approximately nine years under an operating lease.

Deferred_charges

Deferred charges	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Deferred charges	7	Deferred charges:
			Dry-docking			Financing			Total
						fees
	December 31, 2012		$	12,694		$	31,122		$	43,816
	Cost incurred			3,500			25,131			28,631
	Amortization expensed(a)			(3,947	)		(9,477	)		(13,424	)
	Refinancing expenses and costs(b)			—			(4,038	)		(4,038	)
	Amortization capitalized			—			(1,014	)		(1,014	)
	December 31, 2013		$	12,247		$	41,724		$	53,971
	Cost incurred			11,318			19,445			30,763
	Amortization expensed(a)			(5,059	)		(10,342	)		(15,401	)
	Refinancing expenses and recoveries(b)			—			(3,279	)		(3,279	)
	Amortization capitalized			—			(1,399	)		(1,399	)
	December 31, 2014		$	18,506		$	46,149		$	64,655
		(a)	Amortization of dry-docking amounts is included in depreciation and amortization. Amortization of financing fees is included in amortization of deferred charges, unless it qualifies for capitalization.
		(b)	In December 2014, the Company negotiated an early termination of its lease financing structure related to five 4500 TEU vessels. In connection with the early termination, the Company wrote off deferred financing fees of approximately $945,000.
	On April 3, 2014, the Company issued senior unsecured notes for gross proceeds of $345,000,000. A portion of these proceeds was used to repay its $125,000,000 credit facility. As a result, the Company incurred refinancing expenses and costs of approximately $2,334,000.
	In December 2013, the Company entered into an agreement to extend and refinance its $1.0 billion revolving credit facility, or the Facility (note 10). In connection with the refinancing, the Company incurred refinancing expenses and costs of approximately $4,038,000.

Other_assets

Other assets	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other assets	8	Other assets:
			2014		2013
	Equity investment in affiliate(a)		$	19,555	$	4,299
	Restricted cash(b)			13,855		73,855
	Intangible assets			2,525		2,695
	Capital assets			1,579		471
	Other			29,794		25,624
	Other assets		$	67,308	$	106,944
		(a)	On March 14, 2011, the Company entered into an agreement to participate in GCI, an investment vehicle established by an affiliate of The Carlyle Group. GCI will invest up to $900,000,000 equity capital in containership assets strategic to the People’s Republic of China, Taiwan, Hong Kong and Macau. The Company agreed to make a minority investment in GCI of up to $100,000,000 during the investment period, which is anticipated to be up to five years. The Company accounts for its 10.8% investment in GCI using the equity method. The investment of $19,555,000 is comprised of the Company’s capital contribution of $21,408,000 (2013—$6,408,000) less its cumulative equity loss on investment of $1,853,000 (2013—$2,109,000).
		(b)	Included in this amount is nil (2013—$60,000,000) which was placed in a deposit account over which the former lessor had a first priority interest (note 11(a)(i)).

Deferred_revenue

Deferred revenue	12 Months Ended
	Dec. 31, 2014
Revenue Recognition [Abstract]
Deferred revenue	9	Deferred revenue:
			2014			2013
	Deferred revenue on time charters		$	21,889		$	21,099
	Deferred interest on lease receivable			4,143			7,903
	Other deferred revenue			8,982			2,824
	Deferred revenue			35,014			31,826
	Current portion			(27,671	)		(27,683	)
	Deferred revenue		$	7,343		$	4,143

Longterm_debt

Long-term debt	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Long-term debt	10	Long-term debt:
			2014			2013
	Long-term debt:
	Revolving credit facilities(a)		$	1,301,920		$	2,268,841
	Term loan credit facilities(b)			1,735,499			972,777
	Senior unsecured notes(c)			345,000			—
	Long-term debt			3,382,419			3,241,618
	Current portion			(298,010	)		(388,159	)
	Long-term debt		$	3,084,409		$	2,853,459
		(a)	Revolving credit facilities:
	As of December 31, 2014, the Company had four long-term revolving credit facilities (“Revolvers”) available and a line of credit, which provided for aggregate borrowings of up to $1,307,046,000 (2013—$2,388,284,000), of which $5,126,000 (2013—$119,443,000) was undrawn. One of the term loan credit facilities (“Term Loans”) has a revolving loan component and this component has been included in the Revolvers.
	At December 2013, the Company had an outstanding balance of approximately $1.0 billion under a revolving credit facility that matures in May 2015. In December 2013, the Company entered into an agreement to extend and refinance the Facility. Effective January 31, 2014, the maturity date for the Facility was extended from May 2015 to May 2019, the outstanding amount of the Facility was reduced to $433,800,000 and the margin was increased. The reduction in the outstanding amount of the Facility was funded by drawing $340,000,000 under existing credit facilities, one of which is secured by certain vessels that were pledged as collateral under the Facility, and approximately $260,000,000 of cash on hand.
	On March 27, 2014, the Company cancelled its $150,000,000 revolving credit facility. No amounts were drawn under this facility as of that date.
	On May 1, 2014, the Company entered into a 364-day unsecured revolving credit facility with various banks for up to $100,000,000. The facility bears interest at LIBOR plus a margin. At December 31, 2014, $100,000,000 has been drawn under this facility.
	The Revolvers mature between April 30, 2015 and December 31, 2023.
	Based on the Revolvers outstanding at December 31, 2014, the minimum repayments for the balances outstanding are as follows:
	2015		$	167,593
	2016			70,417
	2017			111,201
	2018			73,355
	2019			205,188
	Thereafter			674,166
			$	1,301,920
	Interest is calculated as one month or three month LIBOR plus a margin per annum, depending on the interest period selected by the Company. At December 31, 2014, the one month and three month LIBOR was 0.2% (2013—0.2%) and the margins ranged between 0.5% and 1.3% (2013—0.5% and 0.9%). The weighted average rate of interest, including the margin, was 0.8% at December 31, 2014 (2013—0.8%).
	The Company is subject to commitment fees ranging between 0.2% and 0.4% calculated on the undrawn amounts under the various facilities.
	The Revolver loan payments are made in quarterly or semi-annual payments commencing six or thirty-six months after delivery of the associated newbuilding containership.
		(b)	Term loan credit facilities:
	As of December 31, 2014, the Company had 13 Term Loans available, which provided for aggregate borrowings of up to $2,075,499,000 (2013—$1,739,497,000), of which $340,000,000 (2013—$766,720,000) was undrawn. One of the Term Loans has a revolving loan component and this component has been included in the Revolvers.
	On June 30, 2014, the Company entered into a term loan facility with a European bank for up to $83,000,000 to finance the construction of one newbuilding containership. The loan bears interest at LIBOR plus a margin. At December 31, 2014, no amount has been drawn under this facility.
	On December 24, 2014, the Company entered into a term loan facility with a U.S. bank and an Australian bank for up to $67,040,000 to re-finance the purchase of two 4500 TEU containerships. The loan bears interest at LIBOR plus a margin. At December 31, 2014, $67,040,000 has been drawn under this facility.
	The Term Loans mature between July 9, 2017 and April 23, 2025.
	Based on the Term Loans outstanding at December 31, 2014, the minimum repayments for the balances outstanding are as follows:
	2015		$	130,417
	2016			140,207
	2017			164,757
	2018			142,905
	2019			355,249
	Thereafter			801,964
			$	1,735,499
	For certain of our Term Loans with a total principal outstanding of $1,614,394,000 interest is calculated as one month, three month or six month LIBOR plus a margin per annum, depending on the interest period selected by the Company. At December 31, 2014, the one month, three month and six month LIBOR was 0.2%, 0.2% and 0.3%, respectively (2013—0.2%, 0.2% and 0.4%, respectively) and the margins ranged between 0.4% and 4.8% (2013—0.4% and 4.8%).
	For certain of our Term Loans with a total principal outstanding of $116,605,000, interest is calculated based on the Export-Import Bank of Korea (KEXIM) plus 0.7% per annum.
	For certain of our Term Loans with a total principal outstanding of $4,500,000, the loans bear interest of 6% per annum.
	The weighted average rate of interest, including the margin, was 2.8% at December 31, 2014 (2013— 2.7%).
	The Company is subject to commitment fees ranging between 0.2% and 1.1% calculated on the undrawn amounts under the various facilities.
	The Term Loan payments are made in quarterly or semi-annual payments commencing three, six or thirty-six months after delivery of the associated newbuilding containership or utilization date. For certain of our Term Loans with a total principal outstanding of $4,500,000 payment is due on the third anniversary of the delivery date of the underlying vessel.
		(c)	Senior unsecured notes:
	On April 3, 2014, the Company issued 13,800,000 senior unsecured notes (“the Notes”) at a price of $25.00 per note for gross proceeds of $345,000,000. A portion of the Notes were used to repay a $125,000,000 term loan credit facility. The Notes mature on April 30, 2019 and bear interest at a rate of 6.375% per annum, payable quarterly.
		(d)	General:
	The security for each of the Company’s current credit facilities, except for unsecured term loans, includes:
		•		A first priority mortgage on the collateral vessels funded by the related credit facility;
		•		An assignment of the Company’s time charters and earnings related to the related collateral vessels;
		•		An assignment of the insurance on each of the vessels that are subject to a related mortgage;
		•		An assignment of the Company’s related shipbuilding contracts; and
		•		A pledge of the related retention accounts.
	The Company may prepay certain amounts outstanding without penalty, other than breakage costs in certain circumstances. Under each of our credit facilities, in certain circumstances a prepayment may be required as a result of certain events including the sale or loss of a vessel, a termination or expiration of a charter (and the inability to enter into a charter suitable to lenders within a period of time) or termination of a shipbuilding contract. The amount that must be prepaid may be calculated based on the loan to market value ratio or some other ratio that takes into account the market value of the relevant vessels.
	In these circumstances, valuations of our vessels are conducted on a “without charter” basis as required under the relevant credit facility agreement. Amounts prepaid in accordance with these provisions may be re-borrowed, subject to certain conditions.
	Each credit facility contains financial covenants requiring the Company maintain minimum liquidity, tangible net worth, interest coverage ratios, interest and principal coverage ratios, and debt to assets ratios, as defined. The Company is in compliance with these covenants at December 31, 2014.

Other_longterm_liabilities

Other long-term liabilities	12 Months Ended
	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Other long-term liabilities	11	Other long-term liabilities:
			2014			2013
	Long term obligations under capital lease(a)		$	214,458		$	611,603
	Deferred gain on sale-leasebacks(c)			57,627			—
	Other long-term liabilities			272,085			611,603
	Current portion			(18,543	)		(38,930	)
			$	253,542		$	572,673
		(a)	Long-term obligations under capital lease:
	The Company, through certain of its wholly-owned subsidiaries, has entered into non-recourse or limited recourse sale-leaseback arrangements with financial institutions to fund the construction of certain vessels under existing shipbuilding contracts.
	Under these arrangements, the Company has agreed to transfer the vessels to the lessors and, commencing on the delivery date of the vessels by the shipyard, lease the vessels back from the lessor over the applicable lease term. In the arrangements where the shipbuilding contracts are novated to the lessors, the lessors assume responsibility for the remaining payments under the shipbuilding contracts.
	The leases are accounted for as capital leases. The vessels are recorded as an asset and the lease obligations are recorded as a liability.
	In certain of the arrangements, the lessors are companies whose only assets and operations are to hold the Company’s leases and vessels. The Company operates the vessels during the lease term and supervises the vessels’ construction before the lease term begins. As a result, the Company is considered to be the primary beneficiary of the lessors and consolidates the lessors for financial reporting purposes. The terms of the leases are as follows:
		(i)	Leases for five 4500 TEU vessels:
	Under this lease financing arrangement, the Company had five leases with a subsidiary of a financial institution. The leases were five-year terms that commenced between October 2010 and August 2011. In December 2014, the Company negotiated an early termination of the lease financing structure and, through a series of agreements, regained legal title to the vessels. As a result, the Company paid the termination amounts, funded by cash and the $60,000,000 that was in a cash deposit account over which the lessor had a first priority interest, realized a net gain of $3,763,000 and wrote off deferred financing fees of $945,000.
		(ii)	COSCO Pride—13100 TEU vessel:
	Under this arrangement, the lessor has provided financing of $144,185,000. The term of the lease is 12 years beginning June 29, 2011, which was the vessel’s delivery date. Lease payments include an interest component based on three month LIBOR plus a 2.6% margin. At the end of the lease, the outstanding balance of up to $48,000,000 will be due and title of the vessel will transfer to the Company.
		(iii)	COSCO Faith—13100 TEU vessel:
	Under this arrangement, the lessor has provided financing of $109,000,000. The term of the lease is 12 years beginning March 14, 2012, which was the vessel’s delivery date. Lease payments include an interest component based on three month LIBOR plus a 3.0% margin. At the end of the lease, the Company will have the option to purchase the vessel from the lessor for $1.
	As of December 31, 2014, the carrying value of the two vessels funded under remaining facilities was $315,600,000 (2013—7 vessels $766,321,000).
		(b)	Based on maximum amounts funded, payments due to the lessors would be as follows:
	2015		$	20,226
	2016			23,044
	2017			23,387
	2018			23,731
	2019			24,101
	Thereafter			146,794
				261,283
	Less amounts representing interest			(46,825	)
			$	214,458
		(c)	Deferred gain on sale-leaseback:
	During 2014, the Company entered into lease financing arrangements with Asian special purpose companies (“SPCs”) for four 10000 TEU newbuilding vessels that are chartered to Mitsui O.S.K. Lines Ltd. (“MOL”). The lease financing arrangements are expected to provide gross financing proceeds of approximately $110,000,000 per vessel or $440,000,000 in total, upon delivery of the vessels. Under the lease financing arrangements, the Company will sell the vessels to the SPCs and lease the vessels back from the SPCs over a term of approximately 8.5 years, with an option to purchase the vessels at the end of the lease term for a pre-determined fair value purchase price. If the purchase option is not exercised, the lease term will be automatically extended for an additional two years.
	During 2014, the Company financed three of the vessels through the lease financing arrangements, received gross proceeds of $330,000,000 and recorded a total deferred gain of $59,055,000 on the sale-leasebacks. The deferred gain will be recorded as a reduction of the related operating lease expense over 10.5 years, representing the initial lease term of 8.5 years plus the two year extension.

Share_capital

Share capital	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Share capital	12	Share capital:
		(a)	Common shares:
	In addition to Class A common shares, the Company has 25,000,000 Class B common shares and 100 Class C common shares authorized. For each of these classes of common shares, there are nil shares issued and outstanding at December 31, 2014 (2013—nil).
	The Company has a dividend reinvestment program (“DRIP”) that allows interested shareholders to reinvest all or a portion of cash dividends received on the Company’s common shares. If new common shares are issued by the Company, the reinvestment price is equal to the average price of the Company’s common shares for the five days immediately prior to the reinvestment, less a discount. The discount rate is set by the Board of Directors and is currently 3%. If common shares are purchased in the open market, the reinvestment price is equal to the average price per share paid.
	On May 22, 2014, the Company announced that it had entered into an equity distribution agreement with sales agents under which the Company may, from time to time, issue Class A common shares in one or more at-the-market (“ATM”) offerings up to an aggregate of $75,000,000 in gross sales proceeds. Sales of such Class A common shares will be made by means of ordinary brokers’ transactions on the New York Stock Exchange at market prices, in block transactions, or as otherwise agreed between the Company and the sales agents. During the year ended December 31, 2014, the Company issued 206,600 Class A common shares under the ATM program for gross proceeds of $4,733,000.
	On November 25, 2013, the Company issued 3,500,000 Class A common shares at a price of $22.00 per share for gross proceeds of approximately $77,000,000.
	On February 26, 2012, the Company adopted an open market share repurchase plan of up to $50,000,000 of its Class A common shares. During the year ended December 31, 2012, 148,101 Class A common shares were repurchased via the open market repurchase plan for $2,203,000.
	On January 19, 2012, the Company accepted the re-purchase of 11,300,000 Class A common shares at a price of $15.00 per share, for an aggregate cost of $170,609,000 including fees and expenses of $1,110,000 relating to the tender offer.
		(b)	Preferred shares:
	On January 28, 2014, the Company held a special meeting of shareholders and approved an increase to the number of the Company’s authorized shares of preferred stock from 65,000,000 to 150,000,000 with a corresponding increase in the number of authorized shares of capital stock from 290,000,100 to 375,000,100.
	As at December 31, 2014, the Company had the following preferred shares outstanding:
							Liquidation preference
			Shares				December  31,		December  31,
	Series		Authorized		Issued		2014		2013
	A			315,000		—	$	—	$	344,262
	B			260,000		—		—		—
	C			40,000,000		13,665,531		341,638		341,638
	D			20,000,000		5,105,000		127,625		127,625
	E			15,000,000		5,400,000		135,000		—
	R			1,000,000		—		—		—
		(i)	Series A preferred shares:
	On January 30, 2014, the Company’s outstanding 200,000 Series A preferred shares automatically converted into a total of 23,177,175 Class A common shares.
		(ii)	Series C preferred shares:
	The Series C preferred shares were issued for cash and pay cumulative quarterly dividends at a rate of 9.5% per annum from their date of issuance. At any time on or after January 30, 2016, the Series C preferred shares may be redeemed, in whole or in part at a redemption price of $25.00 per share plus unpaid dividends. If the Company fails to comply with certain covenants, default on any of its credit facilities, fails to pay dividends or if the Series C preferred shares are not redeemed at the option of the Company, in whole by January 30, 2017, the dividend rate payable on the Series C preferred shares increases quarterly, subject to an aggregate maximum rate per annum of 25% prior to January 30, 2016 and 30% thereafter, to a rate that is 1.25 times the dividend rate payable on the Series C preferred shares. The Series C preferred shares are not convertible into common shares and are not redeemable at the option of the holder.
	In September 2013, the Company repurchased 320,000 of its 9.5% Series C Preferred Shares at $26.50 per share for a total of approximately $8,560,000. On September 11, 2013, the Company authorized the repurchase of up to $25,000,000 of its 9.5% Series C preferred shares. The share repurchase authorization expired in July 2014. During the year ended December 31, 2014, nil Series C preferred shares (2013—14,469) were repurchased for a total of approximately nil (2013—$390,000) via the open market repurchase plan.
		(iv)	Series D preferred shares:
	On December 13, 2012, the Company issued 3,105,000 Series D preferred shares for gross proceeds of $77,625,000. On November 8, 2013, the Company issued an additional 2,000,000 Series D preferred shares for gross proceeds of $50,000,000. The Series D preferred shares were issued for cash and pay cumulative quarterly dividends at a rate of 7.95% per annum from their date of issuance. At any time on or after January 30, 2018, the Series D preferred shares may be redeemed by the Company, in whole or in part at a redemption price of $25.00 per share plus unpaid dividends. The Series D preferred shares are not convertible into common shares and are not redeemable at the option of the holder.
		(v)	Series E preferred shares:
	On February 13, 2014, the Company issued 5,400,000 Series E preferred shares for gross proceeds of $135,000,000. The Series E preferred shares were issued for cash and pay cumulative quarterly dividends at a rate of 8.25% per annum from their date of issuance. At any time on or after February 13, 2019, the Series E preferred shares may be redeemed by the Company, in whole or in part at a redemption price of $25.00 per share plus unpaid dividends. The Series E preferred shares are not convertible into common shares and are not redeemable at the option of the holder.

Earnings_per_share

Earnings per share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings per share	13	Earnings per share:
		(a)	Earnings per share computation:
	The Company applies the if-converted method to determine the EPS impact for the convertible Series A preferred shares for those periods prior to the conversion of the Series A preferred shares on January 30, 2014. The following is a reconciliation of the numerator and denominator used in the basic and diluted EPS computations.
	For the year ended December 31, 2014		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	131,247
	Less:
	Preferred share dividends:
	Series A			(3,395	)
	Series C			(33,623	)
	Series D			(10,036	)
	Series E			(9,776	)
	Basic EPS:
	Earnings attributable to common shareholders		$	74,417			93,402,000	$	0.8
	Effect of dilutive securities:
	Share-based compensation			—			131,000
	Contingent consideration			—			117,000
	Diluted EPS(1):
	Earnings attributable to common shareholders		$	74,417			93,650,000	$	0.79
	For the year ended December 31, 2013		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	299,028
	Less:
	Preferred share dividends:
	Series A			(38,390	)
	Series C			(34,035	)
	Series D			(6,744	)
	Series C preferred share repurchases			(660	)
	Basic EPS:
	Earnings attributable to common shareholders		$	219,199			65,273,000	$	3.36
	Effect of dilutive securities:
	Share-based compensation			—			306,000
	Contingent consideration			—			567,000
	Shares held in escrow			—			47,000
	Convertible Series A preferred shares			38,390			21,641,000
	Diluted EPS:
	Earnings attributable to common shareholders plus assumed conversion		$	257,589			87,834,000	$	2.93
	For the year ended December 31, 2012		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	121,305
	Less:
	Preferred share dividends:
	Series A			(34,195	)
	Series C			(34,112	)
	Series D			(309	)
	Basic EPS:
	Earnings attributable to common shareholders		$	52,689			62,923,240	$	0.84
	Effect of dilutive securities:
	Share-based compensation			—			238,000
	Contingent consideration			—			1,236,000
	Shares held in escrow			—			545,000
	Diluted EPS(1):
	Earnings attributable to common shareholders plus assumed conversion		$	52,689			64,942,240	$	0.81
		-1	The convertible Series A preferred shares are not included in the computation of diluted EPS because their effects are anti-dilutive for the period the shares were outstanding.

Sharebased_compensation

Share-based compensation	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based compensation	14	Share-based compensation:
	In December 2005, the Company’s Board of Directors adopted the Seaspan Corporation Stock Incentive Plan (the “Plan”), under which our officers, employees and directors may be granted options, restricted shares, phantom shares, and other stock-based awards as may be determined by the Company’s Board of Directors. A total of 2,000,000 shares of common stock are reserved for issuance under the Plan, which is administered by the Company’s Board of Directors. The Plan expires ten years from the date of its adoption. At December 31, 2014, there are 578,598 (2013—764,848) remaining shares left for issuance under this Plan.
	A summary of the Company’s outstanding restricted shares, phantom share units, SARs and restricted stock units as of December 31, 2014 is presented below:
			Restricted shares					Phantom share units					Stock appreciation rights					Restricted stock units
			Number			W.A. grant		Number			W.A. grant		Number of			W.A. grant		Number			W.A. grant
			of shares			date FV		of units			date FV		SARs			date FV		of units			date FV
	December 31, 2011			43,200		$	13.04		522,000		$	12.78		—		$	—		—		$	—
	Granted			63,653			14.17		40,000			17.68		5,674,148			2.03		—			—
	Vested			(43,200	)		13.04		—			—		—			—		—			—
	December 31, 2012			63,653			14.17		562,000			13.13		5,674,148			2.03		—			—
	Granted			54,990			17.01		95,000			19.3		1,664,457			3.51		—			—
	Vested			(65,578	)		14.25		—			—		—			—		—			—
	Exercised			—			—		—			—		(241,906	)		3.65		—			—
	Cancelled			(4,185	)		17.01		—			—		(23,754	)		3.51		—			—
	December 31, 2013			48,880			17.01		657,000			14.02		7,072,945			2.32		—			—
	Granted			43,936			22.57		70,000			23.04		—			—		72,314			23.03
	Vested			(48,880	)		17.01		—			—		—			—		(37,238	)		23.03
	Exercised			—			—		—			—		(1,193,529	)		2.42		—			—
	Exchanged			—			—		(20,000	)		19		—			—		—			—
	Cancelled
	December 31, 2014			43,936		$	22.57		707,000		$	14.77		5,879,416		$	2.3		35,076		$	23.03
	During 2014, the Company recognized $7,701,000 (2013—$14,004,000; 2012—$3,278,000) in compensation cost related to the above share-based compensation awards.
	At December 31, 2014, there was $3,041,000 (2013—$6,472,000) of total unrecognized compensation costs relating to unvested share-based compensation awards which are expected to be recognized over a weighted average period of 18 months.
		(i)	Restricted shares and phantom share units:
	Class A common shares are issued on a one for one basis in exchange for the cancellation of vested restricted shares and phantom share units. The restricted shares generally vest over one year and the phantom share units generally vest over three years. During 2014, the total fair value of restricted shares vested was $831,000 (2013—$935,000; 2012—$563,000) and the total fair value of shares cancelled was nil (2013—$71,000; 2012—nil).
	As vested outstanding phantom share units are only exchanged for common shares upon written notice from the holder, the phantom share units that are exchanged for common shares may include units that vested in prior periods. At December 31, 2014, 560,000 (2013—460,000) of the outstanding phantom share units were vested and available for exchange by the holder.
		(ii)	Share appreciation rights:
	On December 7, 2012, the Company granted 5,674,148 SARs to an executive of the Company which vest and become exercisable in three tranches when and if the fair market value of the common shares equals or exceeds the applicable base price for each tranche for any 20 consecutive trading days on or before the expiration date of each tranche. The executive may exercise each vested tranche of SARs and receive common shares with a value equal to the difference between the applicable base price and the fair market value of the common shares on the exercise date.
	On March 27, 2013, the Company granted 1,664,457 SARs to certain members of management (the “Participants”) which vest and become exercisable in three tranches when and if the fair market value of the common shares equals or exceeds the applicable base price for each tranche for any 20 consecutive trading days on or before the expiration date of each tranche. The Participants may exercise each vested tranche of SARs and receive common shares with a value equal to the difference between the applicable base price and the fair market value of the common shares on the exercise date. The common shares received on the exercise of SARs are subject to a retention requirement where the Participant is required to retain ownership of 50% of the net after tax number of shares until the later of March 22, 2018 or 120 days after the exercise date.
	The assumptions used in the Monte Carlo model to calculate the grant date fair value of the SARs were as follows:
			2013			2012
	Average expected term			3.8 years			1.5 years
	Expected volatility			39.73%			40.12%
	Dividend yield			4.97%			5.74%
	Average risk free rate			0.50%			0.47%
	The following table provides information about the three tranches of SARs granted:
								Number of SARs granted
			Base price			Expiration date		2013			2012
	Tranche 1		$	21.5			December 7, 2015		531,885			1,846,154
	Tranche 2			24			7-Dec-16		556,946			1,898,734
	Tranche 3			26.5			7-Dec-17		575,626			1,929,260
	Total								1,664,457			5,674,148
		(iii)	Restricted stock units:
	On June 12, 2014, under the Company’s Cash and Share Bonus Plan, the Company granted a total of 72,314 restricted stock units to eligible participants, of which 39,399 restricted stock units relate to 2012 and 32,915 restricted stock units relate to 2013. The restricted stock units generally vest over three years, in equal one-third amounts on each anniversary date of the date of the grant. The restricted stock units are valued at the market price of the underlying securities on the grant date and the compensation expense, based on the estimated number of awards expected to vest, is recognized over the three-year vesting period. Upon vesting of the restricted stock units, the participant will receive shares.
		(iv)	Other share-based awards:
	During the year the Company incurred $7,323,000 (2013—$3,532,000; 2012—$123,000) in transaction fees that were capitalized to vessels of which $3,662,000 (2013—$1,766,000; 2012—$62,000) were paid in Class A common shares.
	During the year the Company incurred $4,520,000 (2013—$6,631,000; 2012—$1,790,000) in arrangement fees that were primarily capitalized to deferred financing fees of which $2,260,000 (2013—$2,666,000; 2012—$895,000) were paid in Class A common shares.
	The Company also recognized $600,000 (2013—$600,000; 2012—$750,000) in share-based compensation expenses related to the accrued portion of performance based bonuses that are expected to be settled in stock-based awards in future periods. The number of shares issued under each of these arrangements are based on volume weighted average share prices as defined in the underlying agreements.

Other_information

Other information	12 Months Ended
	Dec. 31, 2014
Additional Financial Information Disclosure [Abstract]
Other information	15	Other information:
		(a)	Accounts payable and accrued liabilities:
	The principal components of accounts payable and accrued liabilities are:
			2014		2013
	Due to related parties (note 4)		$	6,788	$	611
	Accrued interest			20,723		22,273
	Accounts payable and other accrued liabilities			37,697		42,750
			$	65,208	$	65,634
		(b)	Supplemental cash flow information:
			2014		2013		2012
	Interest paid on debt		$	91,450	$	59,999	$	64,123
	Interest received			1,211		1,265		634
	Undrawn credit facility fee paid			3,512		1,656		900
	Non-cash transactions:
	Long-term debt for vessels under construction			161,420		54,080		71,400
	Dividends on Series A preferred shares			3,395		38,390		34,195
	Dividend reinvestment			64,697		31,961		7,168
	Loan repayment for vessels under construction			29,680		6,560		—
	Arrangement and transaction fees (note 14)			6,753		3,342		1,141
	Vessel reallocation (note 4)			11,533		—		—
	Fair value of financial instruments			50,278		—		—
	Capital contribution through loans to affiliate			15,000		—		—
	Other long-term liabilities for vessels under construction			—		—		84,787
	Acquisition of the Manager for shares, excluding cash received			—		—		82,607
	Proceeds on sale of vessel			—		—		52,104

Commitments_and_contingent_obl

Commitments and contingent obligations	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and contingent obligations	16	Commitments and contingent obligations:
		(a)	As of December 31, 2014, the minimum future revenues to be received on committed time charter party agreements and interest income from sales-type capital leases are approximately:
	2015		$	799,800
	2016			836,448
	2017			786,780
	2018			771,564
	2019			743,100
	Thereafter			2,482,431
				$6,420,123
	The minimum future revenues are based on 100% utilization, relate to committed time charter party agreements currently in effect and assume no renewals or extensions.
		(b)	As of December 31, 2014, based on the contractual delivery dates, the Company has outstanding commitments for installment payments for vessels under construction as follows:
	2015		$	651,469
	2016			402,622
			$	1,054,091
		(c)	As of December 31, 2014, the commitment under operating leases for vessels is $320,020,000 for 2015 to 2025 and office space is $8,311,000 for 2015 to 2019. Total commitments under these leases are as follows:
	2015		$	32,794
	2016			33,079
	2017			33,504
	2018			33,172
	2019			32,738
	Thereafter			163,044
				$328,331

Concentrations

Concentrations	12 Months Ended
	Dec. 31, 2014
Risks and Uncertainties [Abstract]
Concentrations	17	Concentrations:
	The Company’s revenue is derived from the following customers:
			2014		2013		2012
	COSCON		$	303,357	$	301,842	$	281,469
	CSCL Asia			126,399		134,434		151,658
	Hapag Lloyd			77,675		65,463		58,980
	K-Line			76,130		76,148		76,359
	Other			133,609		99,203		92,328
			$	717,170	$	677,090	$	660,794

Financial_instruments

Financial instruments	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Financial instruments	18	Financial instruments:
		(a)	Fair value:
	The carrying values of cash and cash equivalents, short-term investments, restricted cash, accounts receivable, loans to affiliate and accounts payable and accrued liabilities approximate their fair values because of their short term to maturity. As of December 31, 2014, the fair value of the Company’s Revolving and Term loan credit facilities is $2,911,330,000 (2013—$2,897,650,000) and the carrying value is $3,037,419,000 (2013—$3,241,618,000). As of December 31, 2014, the fair value of the Company’s other long-term liabilities, excluding the deferred gains, is $217,134,000 (2013—$587,733,000) and the carrying value is $214,458,000 (2013—$611,603,000). The fair value of the Revolving credit facilities, Term loan credit facilities and other long-term liabilities, excluding the deferred gains, are estimated based on expected principal repayments and interest, discounted by relevant forward rates plus a margin appropriate to the credit risk of the Company. Therefore, the Company has categorized the fair value of these financial instruments as Level 3 in the fair value hierarchy.
	As of December 31, 2014, the fair value of the Company’s senior unsecured notes is $342,240,000 (December 31, 2013—nil) and the carrying value is $345,000,000 (December 31, 2013—nil). The fair value of senior unsecured notes is calculated based on a quoted price that is readily and regularly available in an active market. Therefore, the Company has categorized the fair value of these financial instruments as Level 1 in the fair value hierarchy.
	The Company’s interest rate derivative financial instruments are re-measured to fair value at the end of each reporting period. The fair values of the interest rate derivative financial instruments have been calculated by discounting the future cash flow of both the fixed rate and variable rate interest rate payments. The discount rate was derived from a yield curve created by nationally recognized financial institutions adjusted for the associated credit risk. The fair values of the interest rate derivative financial instruments are determined based on inputs that are readily available in public markets or can be derived from information available in publicly quoted markets. Therefore, the Company has categorized the fair value of these derivative financial instruments as Level 2 in the fair value hierarchy.
		(b)	Interest rate derivative financial instruments:
	The Company uses interest rate derivative financial instruments, consisting of interest rate swaps and interest rate swaptions, to manage its interest rate risk associated with its variable rate debt. Prior to 2008, the Company applied hedge accounting to certain of its interest rate swaps. In 2008, the Company voluntarily de-designated all such interest rate swaps as accounting hedges such that the Company no longer applies hedge accounting. The amounts in accumulated other comprehensive loss related to the interest rate swaps to which hedge accounting was previously applied are recognized in earnings when and where the related interest is recognized in earnings.
	As of December 31, 2014, the Company had the following outstanding interest rate derivatives:
	Fixed per		Notional			Maximum			Effective date			Ending date
	annum rate		amount as of			notional
	swapped		December 31,			amount(1)
	for LIBOR		2014
	5.64%		$	714,500		$	714,500			August 31, 2007			August 31,  2017	(2)
	5.42%			438,462			438,462			September 6, 2007			31-May-24
	5.95%			266,944			266,944			January 30, 2014			May 31,  2019	(3)
	5.60%			175,200			175,200			23-Jun-10			December 23,  2021	(2)
	5.03%			111,000			111,000			31-May-07			September 30, 2015
	5.60%			103,500			103,500			28-Aug-09			August 28, 2020
	5.26%			103,500			103,500			3-Jul-06			February 26,  2021	(2)(4)
	5.20%			80,640			80,640			December 18, 2006			October 2, 2015
	5.50%			52,400			52,400			31-Jul-12			July 31, 2019
	5.17%			24,000			24,000			30-Apr-07			May 29, 2020
	5.87%			—			620,390			31-Aug-17			November 28, 2025
		-1	Over the term of the interest rate swaps, the notional amounts increase and decrease. These amounts represent the peak notional over the remaining term of the swap.
		-2	Prospectively de-designated as an accounting hedge in 2008.
		-3	On January 30, 2014, the Company terminated its swap that had an effective date of July 16, 2012 and a pay fixed rate of 5.175% and entered into a new swap with an effective date of January 30, 2014 and a pay fixed rate of 5.945%. The early termination of the swap resulted in a loss of $4,492,000 recorded in change in fair value of financial instruments.
		-4	The Company entered into a swaption agreement with a bank (Swaption Counterparty A) whereby Swaption Counterparty A had the option to require the Company to enter into an interest rate swap to pay LIBOR and receive a fixed rate of 5.26%. This was a European option and was open for a two hour period on February 26, 2014 after which it expired. The notional amount of the underlying swap was $106,800,000 with an effective date of February 28, 2014 and an expiration of February 26, 2021. If Swaption Counterparty A exercised the swaption, the underlying swap would effectively offset the Company’s 5.26% pay fixed LIBOR swap from February 28, 2014 to February 26, 2021. This option was not exercised by Swaption Counterparty A.
	In addition, the Company entered into swaption agreements with a bank (Swaption Counterparty B) whereby Swaption Counterparty B has the option to require the Company to enter into interest rate swaps to pay LIBOR and receive a fixed rate of 1.183% and to pay 0.5% and receive LIBOR, respectively. The notional amounts of the underlying swaps are each $200,000,000 with an effective date of March 2, 2017 and an expiration of March 2, 2027.
	The following table provides information about losses included in net earnings and reclassified from accumulated other comprehensive loss (“AOCL”) into earnings:
			2014			2013			2012
	Gain/(Loss) on derivatives recognized in net earnings:
	Change in fair value of financial instruments		$	(105,694	)	$	60,504		$	(135,998	)
	Loss reclassified from AOCL to net earnings(1)
	Interest expense		$	(4,259	)	$	(5,330	)	$	(8,310	)
	Depreciation and amortization			(1,052	)		(882	)		(836	)
		-1	The effective portion of changes in unrealized loss on interest rate swaps was recorded in accumulated other comprehensive income until September 30, 2008 when these contracts were de-designated as accounting hedges. The amounts in accumulated other comprehensive income will be recognized in earnings when and where the previously hedged interest is recognized in earnings.
	The estimated amount of AOCL expected to be reclassified to net earnings within the next twelve months is approximately $4,402,000.
		(c)	Foreign exchange derivative instruments:
	The Company is exposed to market risk from foreign currency fluctuations. The Company has entered into foreign currency forward contracts to manage foreign currency fluctuations. At December 31, 2014, the notional amount of the foreign exchange forward contracts is $14,200,000 (2013—$12,200,000) and the fair value liability is $638,000 (2013—$286,000).
	Included in short-term investments is $1,100,000 of restricted cash held as collateral for these foreign currency forward contracts.
		(d)	Fair value of asset and liability derivatives:
	The following provides information about the Company’s derivatives:
			2014			2013
	Fair value of financial instruments asset		$	37,677		$	60,188
	Fair value of financial instruments liability			395,443			425,375
	The following provides information about the effect of the master netting agreement:
	December 31, 2014		Gross amounts			Amounts subject			Net amount
			of recognized			to master netting
			assets and			agreement
			liabilities
	Derivative assets		$	37,677		$	26,625		$	11,052
	Derivative liabilities			395,443			26,625			368,818
	Net asset (liability)		$	(357,766	)	$	—		$	(357,766	)
	December 31, 2013		Gross amounts			Amounts subject			Net amount
			of recognized			to master netting
			assets and			agreement
			liabilities
	Derivative assets		$	60,188		$	49,534		$	10,654
	Derivative liabilities			425,375			49,534			375,841
	Net asset (liability)		$	(365,187	)	$	—		$	(365,187	)

Subsequent_events

Subsequent events	12 Months Ended
	Dec. 31, 2014
Subsequent Events [Abstract]
Subsequent events	19	Subsequent events:
		(a)	On January 13, 2015, the Company declared a quarterly dividend of $0.59375, $0.496875 and $0.515625 per Series C, Series D and Series E preferred share, respectively, representing a total distribution of $13,435,000. The dividends were paid on January 30, 2015 to all shareholders of record on January 29, 2015.
		(b)	On January 13, 2015, the Company declared a quarterly dividend of $0.345 per common share. The dividend was paid on January 30, 2015 to all shareholders of record on January 22, 2015. Of the $33,377,000 distribution, $16,310,000 was paid in cash and $17,067,000 was re-invested through the DRIP.

Summary_of_significant_account1

Summary of significant accounting policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Basis of presentation		(a)	Basis of presentation:
	These financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and the following accounting policies have been consistently applied in the preparation of the consolidated financial statements.
Principles of consolidation		(b)	Principles of consolidation:
	The accompanying consolidated financial statements include the accounts of Seaspan Corporation and its wholly-owned subsidiaries. All significant intercompany balances and transactions have been eliminated upon consolidation.
	The Company also consolidates any variable interest entities (“VIEs”) of which it is the primary beneficiary. The primary beneficiary is the enterprise that has both the power to make decisions that most significantly affect the economic performance of the VIE and has the right to receive benefits or the obligation to absorb losses that in either case could potentially be significant to the VIE. The impact of the consolidation of these VIEs is described in note 11.
	The Company accounts for its investment in companies in which it has significant influence by the equity method. The Company’s proportionate share of earnings (loss) is included in earnings and added to or deducted from the cost of the investment.
Foreign currency translation		(c)	Foreign currency translation:
	The functional and reporting currency of the Company is the United States dollar. Transactions involving other currencies are converted into United States dollars using the exchange rates in effect at the time of the transactions. At the balance sheet date, monetary assets and liabilities that are denominated in currencies other than the United States dollar are translated into United States dollars using exchange rates at that date. Exchange gains and losses are included in net earnings.
Cash equivalents		(d)	Cash equivalents:
	Cash equivalents include highly liquid securities with terms to maturity of three months or less when acquired.
Vessels		(e)	Vessels:
	Except as described below, vessels are recorded at their cost, which consists of the purchase price, acquisition and delivery costs, less accumulated depreciation.
	Vessels purchased from the predecessor upon completion of the Company’s initial public offering in 2005 were initially recorded at the predecessor’s carrying value.
	Vessels under construction include deposits, installment payments, interest, financing costs, construction design, supervision costs, and other pre-delivery costs incurred during the construction period.
	Depreciation is calculated on a straight-line basis over the estimated useful life of each vessel, which is 30 years from the date of completion. The Company calculates depreciation based on the estimated remaining useful life and the expected salvage value of the vessel.
	Vessels that are held for use are evaluated for impairment when events or circumstances indicate that their carrying amounts may not be recoverable from future undiscounted cash flows. Such evaluations include the comparison of current and anticipated operating cash flows, assessment of future operations and other relevant factors. If the carrying amount of the vessel exceeds the estimated net undiscounted future cash flows expected to be generated over the vessel’s remaining useful life, the carrying amount of the vessel is reduced to its estimated fair value.
Dry-dock activities		(f)	Dry-dock activities:
	Classification rules require that vessels be dry-docked for inspection including planned major maintenance and overhaul activities for ongoing certification. The Company generally dry-docks its vessels once every five years. Dry-docking activities include the inspection, refurbishment and replacement of steel, engine components, electrical, pipes and valves, and other parts of the vessel. The Company has adopted the deferral method of accounting for dry-dock activities whereby costs incurred are deferred and amortized on a straight-line basis over the period until the next scheduled dry-dock activity.
Goodwill and intangible assets		(g)	Goodwill and intangible assets:
	Goodwill represents the excess of the purchase price of an acquired enterprise over the fair value assigned to assets acquired and liabilities assumed in a business combination. Goodwill is not amortized, but reviewed for impairment annually or more frequently if impairment indicators arise. When goodwill is reviewed for impairment, the Company may elect to assess qualitative factors to determine whether it is more likely than not that the fair value of a reporting unit is less than its carrying amount, including goodwill. Alternatively, the Company may bypass this step and use a fair value approach to identify potential goodwill impairment and, when necessary, measure the amount of impairment. The Company uses a discounted cash flow model to determine the fair value of reporting units, unless there is a readily determinable fair market value.
	Intangible assets with finite lives are amortized over their useful lives. Intangible assets with finite lives are assessed for impairment when and if impairment indicators exist. An impairment loss is recognized if the carrying amount of an intangible asset is not recoverable and its carrying amount exceeds its fair value.
Deferred financing fees		(h)	Deferred financing fees:
	Deferred financing fees represent the unamortized costs incurred on issuance of the Company’s credit and lease facilities. Amortization of deferred financing fees on leases is provided on the effective interest rate method over the term of the underlying obligation. Amortization of deferred financing fees on credit facilities is provided on the effective interest rate method over the term of the facility based on amounts available under the facilities.
Revenue recognition		(i)	Revenue recognition:
	The Company derives its revenues primarily from the charter of its vessels. Each charter agreement is evaluated and classified as an operating or capital lease. For time charters classified as operating leases, revenue for the lease and service components is recognized each day the vessel is on-hire and when collection is reasonably assured.
	For capital leases that are sales-type leases, the difference between the gross investment in lease and the present value of its components, i.e. the minimum lease payments and the estimated residual value, is recorded as unearned lease interest income. The discount rate used in determining the present values is the interest rate implicit in the lease. The present value of the minimum lease payments, computed using the interest rate implicit in the lease, is recorded as the sales price, from which the carrying value of the vessel at the commencement of the lease is deducted in order to determine the profit or loss on sale. Unearned lease interest income is amortized to income over the period of the lease so as to produce a constant periodic rate of return on the net investment in lease.
	Revenue from vessel management is recognized each day the vessel is managed and when collection is reasonably assured.
	Project revenue is recorded on the completed contract basis when the project is substantially complete and the collectability of any outstanding funds is reasonably assured. Funds received from customers prior to substantial completion of the contract are recorded as deferred revenue.
Leases		(j)	Leases:
	Leases, where the Company is the lessee, are classified as either capital leases or operating leases based on an assessment of the terms of the lease.
	For sale-leaseback transactions, the Company, as seller-lessee, would recognize a gain or loss over the term of the lease as an adjustment to the lease expense, unless the loss is required to be recognized immediately by accounting standards. The term of the lease includes the fixed non-cancelable term of the lease plus all renewal periods such that renewal appears reasonably assured.
Derivative financial instruments		(k)	Derivative financial instruments:
	The Company’s hedging policies permit the use of various derivative financial instruments to manage interest rate risk. The Company has entered into interest rate swaps and swaptions to reduce the Company’s exposure to changing interest rates on its credit and lease facilities.
	All of the Company’s derivatives are measured at their fair value at the end of each period. For derivatives not designated as accounting hedges, changes in their fair value are recorded in earnings.
	The Company had previously designated certain of its interest rate swaps as accounting hedges and applied hedge accounting to those instruments. While hedge accounting was applied, the effective portion of the unrealized gains or losses on those designated interest rate swaps was recorded in other comprehensive loss.
	By September 30, 2008, the Company de-designated all of the interest rate swaps it had accounted for as hedges to that date. Subsequent to their de-designation dates, changes in their fair value are recorded in earnings.
	The Company evaluates whether the occurrence of any of the previously hedged interest payments are considered to be remote. When the previously hedged interest payments are not considered remote of occurring, unrealized gains or losses in accumulated other comprehensive income associated with the previously designated interest rate swaps are recognized in earnings when and where the interest payments are recognized. If such interest payments are identified as being remote, the accumulated other comprehensive income balance pertaining to these amounts is reversed through earnings immediately.
Fair value measurement		(l)	Fair value measurement:
	Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (i.e. the “exit price”) in an orderly transaction between market participants at the measurement date. The hierarchy is broken down into three levels based on the observability of inputs as follows:
		•		Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company has the ability to access. Valuation adjustments and block discounts are not applied to Level 1 instruments. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of these products does not entail a significant degree of judgment.
		•		Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly.
		•		Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.
Share-based compensation		(m)	Share-based compensation:
	The Company has granted restricted shares, phantom share units, stock appreciation rights (“SARs”) and restricted stock units to certain of its officers, members of management and directors as compensation. Compensation cost is measured at their grant date fair values. Under this method, restricted shares, phantom share units and restricted stock units are measured based on the quoted market price of the Company’s Class A common shares at date of the grant, and SARs are measured at fair value using the Monte Carlo model. The fair value of each grant is recognized straight-line over the requisite service period.
Earnings per share		(n)	Earnings per share:
	The Company had multiple classes of common shares with different participation rights and applied the two-class method to compute basic earnings per share (“EPS”) until the acquisition and cancellation of those shares in January 2012.
	The treasury stock method is used to compute the dilutive effect of the Company’s share-based compensation awards. Under this method, the incremental number of shares used in computing diluted EPS is the difference between the number of shares assumed issued and purchased using assumed proceeds.
	The if-converted method was used to compute the dilutive effect of the Company’s Series A preferred shares until January 30, 2014, the date the Company’s outstanding 200,000 Series A preferred shares automatically converted into Class A common shares. Under the if-converted method, dividends applicable to the Series A preferred shares were added back to earnings attributable to common shareholders, and the Series A preferred shares and paid-in kind dividends were assumed to have been converted at the share price applicable at the end of the period. The if-converted method was applied to the computation of diluted EPS only if the effect was dilutive.
	The dividends applicable to the Series C, D and E preferred shares reduce the earnings available to common shareholders, even if not declared, since the dividends are cumulative.
Use of estimates		(o)	Use of estimates:
	The preparation of consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the balance sheet dates and the reported amounts of revenue and expenses during the reporting fiscal periods. Areas where accounting judgments and estimates are significant to the Company include the assessment of the vessel useful lives, expected salvage values and the recoverability of the carrying value of vessels which are subject to future market events, carrying value of goodwill and the fair value of interest rate derivative financial instruments and share-based awards. Actual results could differ from those estimates.
Comparative information		(p)	Comparative information:
	Certain information has been reclassified to conform with the financial statement presentation adopted for the current year.
Recent accounting pronouncements		(q)	Recent accounting pronouncements:
	In May 2014, the Financial Accounting Standards Board issued Accounting Standards Update, or ASU 2014-09, Revenue from Contracts with Customers, that introduced a new five-step revenue recognition model to be used to determine how an entity should recognize revenue related to the transfer of goods or services to customers in an amount that reflects the consideration the entity is entitled to receive for those goods or services.
	This ASU also requires disclosures sufficient to enable users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers, including qualitative and quantitative disclosures about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. This standard is effective for fiscal years beginning after December 15, 2016, including interim periods within that reporting period. We are currently evaluating the new guidance to determine the impact it will have on our consolidated financial statements.

Acquisition_of_Seaspan_Managem1

Acquisition of Seaspan Management Services Limited (Tables)	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Aggregate Purchase Price	The aggregate purchase price was $106,518,000, including:
	4,220,728 of the Company’s Class A common shares	$	66,899
	Contingent consideration		18,437
	Settlement of intercompany balances		20,022
	Stock based compensation		1,160
	Aggregate purchase price	$	106,518

Related_party_transactions_Tab

Related party transactions (Tables)	12 Months Ended
	Dec. 31, 2014
Related Party Transactions [Abstract]
Schedule of Income or Expenses with Related Parties		The Company incurred the following income or expenses with related parties:
			2014		2013		2012
	Fees paid:
	Arrangement fees		$	4,520	$	6,631	$	1,790
	Transaction fees			7,323		3,532		123
	Reimbursed expenses			237		72		—
	Income received:
	Interest income			9,888		1,150		—
	Management fees			913		69		—

Gross_investment_in_lease_Tabl

Gross investment in lease (Tables)	12 Months Ended
	Dec. 31, 2014
Leases [Abstract]
Schedule of Gross Investment in Lease
		2014			2013
	Gross investment in lease	$	58,953		$	80,123
	Current portion		(21,170	)		(21,170	)
		$	37,783		$	58,953

Vessels_Tables

Vessels (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Schedule of Vessels
	December 31, 2014	Cost		Accumulated		Net book
				depreciation		value
	Vessels	$	5,708,685	$	894,964	$	4,813,721
	Vessels under construction		282,002		—		282,002
	Vessels	$	5,990,687	$	894,964	$	5,095,723
	December 31, 2013	Cost		Accumulated		Net book
				depreciation		value
	Vessels	$	5,391,713	$	720,814	$	4,670,899
	Vessels under construction		321,372		—		321,372
	Vessels	$	5,713,085	$	720,814	$	4,992,271

Deferred_charges_Tables

Deferred charges (Tables)	12 Months Ended
	Dec. 31, 2014
Text Block [Abstract]
Deferred Charges
			Dry-docking			Financing			Total
						fees
	December 31, 2012		$	12,694		$	31,122		$	43,816
	Cost incurred			3,500			25,131			28,631
	Amortization expensed(a)			(3,947	)		(9,477	)		(13,424	)
	Refinancing expenses and costs(b)			—			(4,038	)		(4,038	)
	Amortization capitalized			—			(1,014	)		(1,014	)
	December 31, 2013		$	12,247		$	41,724		$	53,971
	Cost incurred			11,318			19,445			30,763
	Amortization expensed(a)			(5,059	)		(10,342	)		(15,401	)
	Refinancing expenses and recoveries(b)			—			(3,279	)		(3,279	)
	Amortization capitalized			—			(1,399	)		(1,399	)
	December 31, 2014		$	18,506		$	46,149		$	64,655
		(a)	Amortization of dry-docking amounts is included in depreciation and amortization. Amortization of financing fees is included in amortization of deferred charges, unless it qualifies for capitalization.
		(b)	In December 2014, the Company negotiated an early termination of its lease financing structure related to five 4500 TEU vessels. In connection with the early termination, the Company wrote off deferred financing fees of approximately $945,000.

Other_assets_Tables

Other assets (Tables)	12 Months Ended
	Dec. 31, 2014
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Other Assets
			2014		2013
	Equity investment in affiliate(a)		$	19,555	$	4,299
	Restricted cash(b)			13,855		73,855
	Intangible assets			2,525		2,695
	Capital assets			1,579		471
	Other			29,794		25,624
	Other assets		$	67,308	$	106,944
		(a)	On March 14, 2011, the Company entered into an agreement to participate in GCI, an investment vehicle established by an affiliate of The Carlyle Group. GCI will invest up to $900,000,000 equity capital in containership assets strategic to the People’s Republic of China, Taiwan, Hong Kong and Macau. The Company agreed to make a minority investment in GCI of up to $100,000,000 during the investment period, which is anticipated to be up to five years. The Company accounts for its 10.8% investment in GCI using the equity method. The investment of $19,555,000 is comprised of the Company’s capital contribution of $21,408,000 (2013—$6,408,000) less its cumulative equity loss on investment of $1,853,000 (2013—$2,109,000).
		(b)	Included in this amount is nil (2013—$60,000,000) which was placed in a deposit account over which the former lessor had a first priority interest (note 11(a)(i)).

Deferred_revenue_Tables

Deferred revenue (Tables)	12 Months Ended
	Dec. 31, 2014
Revenue Recognition [Abstract]
Deferred Revenue
		2014			2013
	Deferred revenue on time charters	$	21,889		$	21,099
	Deferred interest on lease receivable		4,143			7,903
	Other deferred revenue		8,982			2,824
	Deferred revenue		35,014			31,826
	Current portion		(27,671	)		(27,683	)
	Deferred revenue	$	7,343		$	4,143

Longterm_debt_Tables

Long-term debt (Tables)	12 Months Ended
	Dec. 31, 2014
Debt Disclosure [Abstract]
Schedule of Long-Term Debt
			2014			2013
	Long-term debt:
	Revolving credit facilities(a)		$	1,301,920		$	2,268,841
	Term loan credit facilities(b)			1,735,499			972,777
	Senior unsecured notes(c)			345,000			—
	Long-term debt			3,382,419			3,241,618
	Current portion			(298,010	)		(388,159	)
	Long-term debt		$	3,084,409		$	2,853,459
		(a)	Revolving credit facilities:
	As of December 31, 2014, the Company had four long-term revolving credit facilities (“Revolvers”) available and a line of credit, which provided for aggregate borrowings of up to $1,307,046,000 (2013—$2,388,284,000), of which $5,126,000 (2013—$119,443,000) was undrawn. One of the term loan credit facilities (“Term Loans”) has a revolving loan component and this component has been included in the Revolvers.
	At December 2013, the Company had an outstanding balance of approximately $1.0 billion under a revolving credit facility that matures in May 2015. In December 2013, the Company entered into an agreement to extend and refinance the Facility. Effective January 31, 2014, the maturity date for the Facility was extended from May 2015 to May 2019, the outstanding amount of the Facility was reduced to $433,800,000 and the margin was increased. The reduction in the outstanding amount of the Facility was funded by drawing $340,000,000 under existing credit facilities, one of which is secured by certain vessels that were pledged as collateral under the Facility, and approximately $260,000,000 of cash on hand.
	On March 27, 2014, the Company cancelled its $150,000,000 revolving credit facility. No amounts were drawn under this facility as of that date.
	On May 1, 2014, the Company entered into a 364-day unsecured revolving credit facility with various banks for up to $100,000,000. The facility bears interest at LIBOR plus a margin. At December 31, 2014, $100,000,000 has been drawn under this facility.
	The Revolvers mature between April 30, 2015 and December 31, 2023.
	Based on the Revolvers outstanding at December 31, 2014, the minimum repayments for the balances outstanding are as follows:
	2015		$	167,593
	2016			70,417
	2017			111,201
	2018			73,355
	2019			205,188
	Thereafter			674,166
			$	1,301,920
	Interest is calculated as one month or three month LIBOR plus a margin per annum, depending on the interest period selected by the Company. At December 31, 2014, the one month and three month LIBOR was 0.2% (2013—0.2%) and the margins ranged between 0.5% and 1.3% (2013—0.5% and 0.9%). The weighted average rate of interest, including the margin, was 0.8% at December 31, 2014 (2013—0.8%).
	The Company is subject to commitment fees ranging between 0.2% and 0.4% calculated on the undrawn amounts under the various facilities.
	The Revolver loan payments are made in quarterly or semi-annual payments commencing six or thirty-six months after delivery of the associated newbuilding containership.
		(b)	Term loan credit facilities:
	As of December 31, 2014, the Company had 13 Term Loans available, which provided for aggregate borrowings of up to $2,075,499,000 (2013—$1,739,497,000), of which $340,000,000 (2013—$766,720,000) was undrawn. One of the Term Loans has a revolving loan component and this component has been included in the Revolvers.
	On June 30, 2014, the Company entered into a term loan facility with a European bank for up to $83,000,000 to finance the construction of one newbuilding containership. The loan bears interest at LIBOR plus a margin. At December 31, 2014, no amount has been drawn under this facility.
	On December 24, 2014, the Company entered into a term loan facility with a U.S. bank and an Australian bank for up to $67,040,000 to re-finance the purchase of two 4500 TEU containerships. The loan bears interest at LIBOR plus a margin. At December 31, 2014, $67,040,000 has been drawn under this facility.
	The Term Loans mature between July 9, 2017 and April 23, 2025.
	Based on the Term Loans outstanding at December 31, 2014, the minimum repayments for the balances outstanding are as follows:
	2015		$	130,417
	2016			140,207
	2017			164,757
	2018			142,905
	2019			355,249
	Thereafter			801,964
			$	1,735,499
	For certain of our Term Loans with a total principal outstanding of $1,614,394,000 interest is calculated as one month, three month or six month LIBOR plus a margin per annum, depending on the interest period selected by the Company. At December 31, 2014, the one month, three month and six month LIBOR was 0.2%, 0.2% and 0.3%, respectively (2013—0.2%, 0.2% and 0.4%, respectively) and the margins ranged between 0.4% and 4.8% (2013—0.4% and 4.8%).
	For certain of our Term Loans with a total principal outstanding of $116,605,000, interest is calculated based on the Export-Import Bank of Korea (KEXIM) plus 0.7% per annum.
	For certain of our Term Loans with a total principal outstanding of $4,500,000, the loans bear interest of 6% per annum.
	The weighted average rate of interest, including the margin, was 2.8% at December 31, 2014 (2013— 2.7%).
	The Company is subject to commitment fees ranging between 0.2% and 1.1% calculated on the undrawn amounts under the various facilities.
	The Term Loan payments are made in quarterly or semi-annual payments commencing three, six or thirty-six months after delivery of the associated newbuilding containership or utilization date. For certain of our Term Loans with a total principal outstanding of $4,500,000 payment is due on the third anniversary of the delivery date of the underlying vessel.
		(c)	Senior unsecured notes:
	On April 3, 2014, the Company issued 13,800,000 senior unsecured notes (“the Notes”) at a price of $25.00 per note for gross proceeds of $345,000,000. A portion of the Notes were used to repay a $125,000,000 term loan credit facility. The Notes mature on April 30, 2019 and bear interest at a rate of 6.375% per annum, payable quarterly.

Other_longterm_liabilities_Tab

Other long-term liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Other Liabilities Disclosure [Abstract]
Schedule of Other Long-Term Liabilities
			2014			2013
	Long term obligations under capital lease(a)		$	214,458		$	611,603
	Deferred gain on sale-leasebacks(c)			57,627			—
	Other long-term liabilities			272,085			611,603
	Current portion			(18,543	)		(38,930	)
			$	253,542		$	572,673
		(a)	Long-term obligations under capital lease:
	The Company, through certain of its wholly-owned subsidiaries, has entered into non-recourse or limited recourse sale-leaseback arrangements with financial institutions to fund the construction of certain vessels under existing shipbuilding contracts.
	Under these arrangements, the Company has agreed to transfer the vessels to the lessors and, commencing on the delivery date of the vessels by the shipyard, lease the vessels back from the lessor over the applicable lease term. In the arrangements where the shipbuilding contracts are novated to the lessors, the lessors assume responsibility for the remaining payments under the shipbuilding contracts.
	The leases are accounted for as capital leases. The vessels are recorded as an asset and the lease obligations are recorded as a liability.
	In certain of the arrangements, the lessors are companies whose only assets and operations are to hold the Company’s leases and vessels. The Company operates the vessels during the lease term and supervises the vessels’ construction before the lease term begins. As a result, the Company is considered to be the primary beneficiary of the lessors and consolidates the lessors for financial reporting purposes. The terms of the leases are as follows:
		(i)	Leases for five 4500 TEU vessels:
	Under this lease financing arrangement, the Company had five leases with a subsidiary of a financial institution. The leases were five-year terms that commenced between October 2010 and August 2011. In December 2014, the Company negotiated an early termination of the lease financing structure and, through a series of agreements, regained legal title to the vessels. As a result, the Company paid the termination amounts, funded by cash and the $60,000,000 that was in a cash deposit account over which the lessor had a first priority interest, realized a net gain of $3,763,000 and wrote off deferred financing fees of $945,000.
		(ii)	COSCO Pride—13100 TEU vessel:
	Under this arrangement, the lessor has provided financing of $144,185,000. The term of the lease is 12 years beginning June 29, 2011, which was the vessel’s delivery date. Lease payments include an interest component based on three month LIBOR plus a 2.6% margin. At the end of the lease, the outstanding balance of up to $48,000,000 will be due and title of the vessel will transfer to the Company.
		(iii)	COSCO Faith—13100 TEU vessel:
	Under this arrangement, the lessor has provided financing of $109,000,000. The term of the lease is 12 years beginning March 14, 2012, which was the vessel’s delivery date. Lease payments include an interest component based on three month LIBOR plus a 3.0% margin. At the end of the lease, the Company will have the option to purchase the vessel from the lessor for $1.
	As of December 31, 2014, the carrying value of the two vessels funded under remaining facilities was $315,600,000 (2013—7 vessels $766,321,000).
		(b)	Based on maximum amounts funded, payments due to the lessors would be as follows:
	2015		$	20,226
	2016			23,044
	2017			23,387
	2018			23,731
	2019			24,101
	Thereafter			146,794
				261,283
	Less amounts representing interest			(46,825	)
			$	214,458
		(c)	Deferred gain on sale-leaseback:
	During 2014, the Company entered into lease financing arrangements with Asian special purpose companies (“SPCs”) for four 10000 TEU newbuilding vessels that are chartered to Mitsui O.S.K. Lines Ltd. (“MOL”). The lease financing arrangements are expected to provide gross financing proceeds of approximately $110,000,000 per vessel or $440,000,000 in total, upon delivery of the vessels. Under the lease financing arrangements, the Company will sell the vessels to the SPCs and lease the vessels back from the SPCs over a term of approximately 8.5 years, with an option to purchase the vessels at the end of the lease term for a pre-determined fair value purchase price. If the purchase option is not exercised, the lease term will be automatically extended for an additional two years.
	During 2014, the Company financed three of the vessels through the lease financing arrangements, received gross proceeds of $330,000,000 and recorded a total deferred gain of $59,055,000 on the sale-leasebacks. The deferred gain will be recorded as a reduction of the related operating lease expense over 10.5 years, representing the initial lease term of 8.5 years plus the two year extension.
Based on Maximum Amounts Funded Payments Under Leases Due to Lessors		(b)	Based on maximum amounts funded, payments due to the lessors would be as follows:
	2015		$	20,226
	2016			23,044
	2017			23,387
	2018			23,731
	2019			24,101
	Thereafter			146,794
				261,283
	Less amounts representing interest			(46,825	)
			$	214,458

Share_capital_Tables

Share capital (Tables)	12 Months Ended
	Dec. 31, 2014
Equity [Abstract]
Schedule of Preferred Shares Outstanding	As at December 31, 2014, the Company had the following preferred shares outstanding:
						Liquidation preference
		Shares				December  31,		December  31,
	Series	Authorized		Issued		2014		2013
	A		315,000		—	$	—	$	344,262
	B		260,000		—		—		—
	C		40,000,000		13,665,531		341,638		341,638
	D		20,000,000		5,105,000		127,625		127,625
	E		15,000,000		5,400,000		135,000		—
	R		1,000,000		—		—		—

Earnings_per_share_Tables

Earnings per share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Reconciliation of Numerator and Denominator Used in Basic and Diluted EPS Computations	The following is a reconciliation of the numerator and denominator used in the basic and diluted EPS computations.
	For the year ended December 31, 2014		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	131,247
	Less:
	Preferred share dividends:
	Series A			(3,395	)
	Series C			(33,623	)
	Series D			(10,036	)
	Series E			(9,776	)
	Basic EPS:
	Earnings attributable to common shareholders		$	74,417			93,402,000	$	0.8
	Effect of dilutive securities:
	Share-based compensation			—			131,000
	Contingent consideration			—			117,000
	Diluted EPS(1):
	Earnings attributable to common shareholders		$	74,417			93,650,000	$	0.79
	For the year ended December 31, 2013		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	299,028
	Less:
	Preferred share dividends:
	Series A			(38,390	)
	Series C			(34,035	)
	Series D			(6,744	)
	Series C preferred share repurchases			(660	)
	Basic EPS:
	Earnings attributable to common shareholders		$	219,199			65,273,000	$	3.36
	Effect of dilutive securities:
	Share-based compensation			—			306,000
	Contingent consideration			—			567,000
	Shares held in escrow			—			47,000
	Convertible Series A preferred shares			38,390			21,641,000
	Diluted EPS:
	Earnings attributable to common shareholders plus assumed conversion		$	257,589			87,834,000	$	2.93
	For the year ended December 31, 2012		Earnings			Shares		Per share
			(numerator)			(denominator)		amount
	Net earnings		$	121,305
	Less:
	Preferred share dividends:
	Series A			(34,195	)
	Series C			(34,112	)
	Series D			(309	)
	Basic EPS:
	Earnings attributable to common shareholders		$	52,689			62,923,240	$	0.84
	Effect of dilutive securities:
	Share-based compensation			—			238,000
	Contingent consideration			—			1,236,000
	Shares held in escrow			—			545,000
	Diluted EPS(1):
	Earnings attributable to common shareholders plus assumed conversion		$	52,689			64,942,240	$	0.81
		-1	The convertible Series A preferred shares are not included in the computation of diluted EPS because their effects are anti-dilutive for the period the shares were outstanding.

Sharebased_compensation_Tables

Share-based compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Outstanding Restricted Shares, Phantom Share Units, SARs and Restricted Stock Units	A summary of the Company’s outstanding restricted shares, phantom share units, SARs and restricted stock units as of December 31, 2014 is presented below:
		Restricted shares					Phantom share units					Stock appreciation rights					Restricted stock units
		Number			W.A. grant		Number			W.A. grant		Number of			W.A. grant		Number			W.A. grant
		of shares			date FV		of units			date FV		SARs			date FV		of units			date FV
	December 31, 2011		43,200		$	13.04		522,000		$	12.78		—		$	—		—		$	—
	Granted		63,653			14.17		40,000			17.68		5,674,148			2.03		—			—
	Vested		(43,200	)		13.04		—			—		—			—		—			—
	December 31, 2012		63,653			14.17		562,000			13.13		5,674,148			2.03		—			—
	Granted		54,990			17.01		95,000			19.3		1,664,457			3.51		—			—
	Vested		(65,578	)		14.25		—			—		—			—		—			—
	Exercised		—			—		—			—		(241,906	)		3.65		—			—
	Cancelled		(4,185	)		17.01		—			—		(23,754	)		3.51		—			—
	December 31, 2013		48,880			17.01		657,000			14.02		7,072,945			2.32		—			—
	Granted		43,936			22.57		70,000			23.04		—			—		72,314			23.03
	Vested		(48,880	)		17.01		—			—		—			—		(37,238	)		23.03
	Exercised		—			—		—			—		(1,193,529	)		2.42		—			—
	Exchanged		—			—		(20,000	)		19		—			—		—			—
	Cancelled
	December 31, 2014		43,936		$	22.57		707,000		$	14.77		5,879,416		$	2.3		35,076		$	23.03
Schedule of Assumptions to Calculate Fair Value of Stock Appreciation Rights	The assumptions used in the Monte Carlo model to calculate the grant date fair value of the SARs were as follows:
		2013			2012
	Average expected term		3.8 years			1.5 years
	Expected volatility		39.73%			40.12%
	Dividend yield		4.97%			5.74%
	Average risk free rate		0.50%			0.47%
Schedule of Information about Three Tranches of SARs Granted	The following table provides information about the three tranches of SARs granted:
							Number of SARs granted
		Base price			Expiration date		2013			2012
	Tranche 1	$	21.5			December 7, 2015		531,885			1,846,154
	Tranche 2		24			7-Dec-16		556,946			1,898,734
	Tranche 3		26.5			7-Dec-17		575,626			1,929,260
	Total							1,664,457			5,674,148

Other_information_Tables

Other information (Tables)	12 Months Ended
	Dec. 31, 2014
Additional Financial Information Disclosure [Abstract]
Schedule of Accounts Payable and Accrued Liabilities		(a)	Accounts payable and accrued liabilities:
	The principal components of accounts payable and accrued liabilities are:
			2014		2013
	Due to related parties (note 4)		$	6,788	$	611
	Accrued interest			20,723		22,273
	Accounts payable and other accrued liabilities			37,697		42,750
			$	65,208	$	65,634
Schedule of Supplemental Cash Flow Information		(b)	Supplemental cash flow information:
			2014		2013		2012
	Interest paid on debt		$	91,450	$	59,999	$	64,123
	Interest received			1,211		1,265		634
	Undrawn credit facility fee paid			3,512		1,656		900
	Non-cash transactions:
	Long-term debt for vessels under construction			161,420		54,080		71,400
	Dividends on Series A preferred shares			3,395		38,390		34,195
	Dividend reinvestment			64,697		31,961		7,168
	Loan repayment for vessels under construction			29,680		6,560		—
	Arrangement and transaction fees (note 14)			6,753		3,342		1,141
	Vessel reallocation (note 4)			11,533		—		—
	Fair value of financial instruments			50,278		—		—
	Capital contribution through loans to affiliate			15,000		—		—
	Other long-term liabilities for vessels under construction			—		—		84,787
	Acquisition of the Manager for shares, excluding cash received			—		—		82,607
	Proceeds on sale of vessel			—		—		52,104

Commitments_and_contingent_obl1

Commitments and contingent obligations (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Revenues to be Received on Committed Agreements		(a)	As of December 31, 2014, the minimum future revenues to be received on committed time charter party agreements and interest income from sales-type capital leases are approximately:
	2015		$	799,800
	2016			836,448
	2017			786,780
	2018			771,564
	2019			743,100
	Thereafter			2,482,431
				$6,420,123
Schedule of Outstanding Commitments for Installment Payments for Vessels		(b)	As of December 31, 2014, based on the contractual delivery dates, the Company has outstanding commitments for installment payments for vessels under construction as follows:
	2015		$	651,469
	2016			402,622
			$	1,054,091
Schedule of Commitment Under Operating Leases		(c)	As of December 31, 2014, the commitment under operating leases for vessels is $320,020,000 for 2015 to 2025 and office space is $8,311,000 for 2015 to 2019. Total commitments under these leases are as follows:
	2015		$	32,794
	2016			33,079
	2017			33,504
	2018			33,172
	2019			32,738
	Thereafter			163,044
				$328,331

Concentrations_Tables

Concentrations (Tables)	12 Months Ended
	Dec. 31, 2014
Risks and Uncertainties [Abstract]
Schedule of Revenue Derived from Customers	The Company’s revenue is derived from the following customers:
		2014		2013		2012
	COSCON	$	303,357	$	301,842	$	281,469
	CSCL Asia		126,399		134,434		151,658
	Hapag Lloyd		77,675		65,463		58,980
	K-Line		76,130		76,148		76,359
	Other		133,609		99,203		92,328
		$	717,170	$	677,090	$	660,794

Financial_instruments_Tables

Financial instruments (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Schedule of Outstanding Interest Rate Derivatives	As of December 31, 2014, the Company had the following outstanding interest rate derivatives:
	Fixed per		Notional			Maximum			Effective date			Ending date
	annum rate		amount as of			notional
	swapped		December 31,			amount(1)
	for LIBOR		2014
	5.64%		$	714,500		$	714,500			August 31, 2007			August 31,  2017	(2)
	5.42%			438,462			438,462			September 6, 2007			31-May-24
	5.95%			266,944			266,944			January 30, 2014			May 31,  2019	(3)
	5.60%			175,200			175,200			23-Jun-10			December 23,  2021	(2)
	5.03%			111,000			111,000			31-May-07			September 30, 2015
	5.60%			103,500			103,500			28-Aug-09			August 28, 2020
	5.26%			103,500			103,500			3-Jul-06			February 26,  2021	(2)(4)
	5.20%			80,640			80,640			December 18, 2006			October 2, 2015
	5.50%			52,400			52,400			31-Jul-12			July 31, 2019
	5.17%			24,000			24,000			30-Apr-07			May 29, 2020
	5.87%			—			620,390			31-Aug-17			November 28, 2025
		-1	Over the term of the interest rate swaps, the notional amounts increase and decrease. These amounts represent the peak notional over the remaining term of the swap.
		-2	Prospectively de-designated as an accounting hedge in 2008.
		-3	On January 30, 2014, the Company terminated its swap that had an effective date of July 16, 2012 and a pay fixed rate of 5.175% and entered into a new swap with an effective date of January 30, 2014 and a pay fixed rate of 5.945%. The early termination of the swap resulted in a loss of $4,492,000 recorded in change in fair value of financial instruments.
		-4	The Company entered into a swaption agreement with a bank (Swaption Counterparty A) whereby Swaption Counterparty A had the option to require the Company to enter into an interest rate swap to pay LIBOR and receive a fixed rate of 5.26%. This was a European option and was open for a two hour period on February 26, 2014 after which it expired. The notional amount of the underlying swap was $106,800,000 with an effective date of February 28, 2014 and an expiration of February 26, 2021. If Swaption Counterparty A exercised the swaption, the underlying swap would effectively offset the Company’s 5.26% pay fixed LIBOR swap from February 28, 2014 to February 26, 2021. This option was not exercised by Swaption Counterparty A.
	In addition, the Company entered into swaption agreements with a bank (Swaption Counterparty B) whereby Swaption Counterparty B has the option to require the Company to enter into interest rate swaps to pay LIBOR and receive a fixed rate of 1.183% and to pay 0.5% and receive LIBOR, respectively. The notional amounts of the underlying swaps are each $200,000,000 with an effective date of March 2, 2017 and an expiration of March 2, 2027.
Schedule of Losses Reclassified from Accumulated Other Comprehensive Loss into Earnings	The following table provides information about losses included in net earnings and reclassified from accumulated other comprehensive loss (“AOCL”) into earnings:
			2014			2013			2012
	Gain/(Loss) on derivatives recognized in net earnings:
	Change in fair value of financial instruments		$	(105,694	)	$	60,504		$	(135,998	)
	Loss reclassified from AOCL to net earnings(1)
	Interest expense		$	(4,259	)	$	(5,330	)	$	(8,310	)
	Depreciation and amortization			(1,052	)		(882	)		(836	)
		-1	The effective portion of changes in unrealized loss on interest rate swaps was recorded in accumulated other comprehensive income until September 30, 2008 when these contracts were de-designated as accounting hedges. The amounts in accumulated other comprehensive income will be recognized in earnings when and where the previously hedged interest is recognized in earnings.
Schedule of Derivatives	The following provides information about the Company’s derivatives:
			2014			2013
	Fair value of financial instruments asset		$	37,677		$	60,188
	Fair value of financial instruments liability			395,443			425,375
Schedule of Financial Instruments, Effect of the Master Netting Agreement	The following provides information about the effect of the master netting agreement:
	December 31, 2014		Gross amounts			Amounts subject			Net amount
			of recognized			to master netting
			assets and			agreement
			liabilities
	Derivative assets		$	37,677		$	26,625		$	11,052
	Derivative liabilities			395,443			26,625			368,818
	Net asset (liability)		$	(357,766	)	$	—		$	(357,766	)
	December 31, 2013		Gross amounts			Amounts subject			Net amount
			of recognized			to master netting
			assets and			agreement
			liabilities
	Derivative assets		$	60,188		$	49,534		$	10,654
	Derivative liabilities			425,375			49,534			375,841
	Net asset (liability)		$	(365,187	)	$	—		$	(365,187	)

General_Additional_Information

General - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Company incorporation date	3-May-05

Summary_of_significant_account2

Summary of significant accounting policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Jan. 30, 2014
Summary Of Significant Accounting Policies [Line Items]
Number of years between dry-docking for each vessel	5 years
Convertible Series A preferred shares, shares	24,170,531	18,970,531
Series A Preferred Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Convertible Series A preferred shares, shares			200,000
Vessels [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of each vessel	30 years

Acquisition_of_Seaspan_Managem2

Acquisition of Seaspan Management Services Limited - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 27, 2012
Business Acquisition [Line Items]
Aggregate purchase price				$106,518,000
Amount deposited in escrow				7,500,000
Shares issued pertaining to contingent consideration arrangement	195,404	820,697
Acquisition-related costs	$0		$1,184,000
Seaspan Management Services Limited [Member]
Business Acquisition [Line Items]
Business acquisition percentage of voting interests acquired				100.00%
Class A Common Shares [Member]
Business Acquisition [Line Items]
Shares deposited in escrow				586,212
Additional contingent consideration				39,081

Acquisition_of_Seaspan_Managem3

Acquisition of Seaspan Management Services Limited - Aggregate Purchase Price (Detail) (USD $)	0 Months Ended
In Thousands, unless otherwise specified	Jan. 27, 2012
Business Combinations [Abstract]
4,220,728 of the Company's Class A common shares	$66,899
Contingent consideration	18,437
Settlement of intercompany balances	20,022
Stock based compensation	1,160
Aggregate purchase price	$106,518

Acquisition_of_Seaspan_Managem4

Acquisition of Seaspan Management Services Limited - Aggregate Purchase Price (Parenthetical) (Detail)	Jan. 27, 2012
Business Combinations [Abstract]
Business acquisition cost of acquired entity number of shares issued	4,220,728

Related_party_transactions_Add

Related party transactions - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Sep. 29, 2014	Dec. 31, 2014	Dec. 31, 2014	Aug. 17, 2014	Dec. 31, 2012	Dec. 31, 2013
	Vessel
Related Party Transaction [Line Items]
Due from related parties, Current		$237,908,000	$237,908,000			$54,068,000
Number of vessels reallocated	2
Capital contribution in equity investee		6,667,000
Amounts due from related parties included in accounts receivable		1,454,000	1,454,000			1,614,000
Related Party Transaction, Description			Arrangement fees and transaction fees are paid either in cash or, at the company's discretion, a combination of cash and up to 50% in the company's common shares (note 14(iv)).
Promissory Note [Member]
Related Party Transaction [Line Items]
Promissory note, issued				25,000,000
Promissory note, interest rate				7.00%
Maximum [Member]
Related Party Transaction [Line Items]
Equity Methods Investment, Percentage			50.00%
GCI [Member]
Related Party Transaction [Line Items]
Due from related parties		237,908,000	237,908,000			53,309,000
Due from related parties, Current						54,068,000
Decrease in the loans to affiliate	9,780,000
Interest receivable on loans to affiliate		9,514,000	9,514,000			759,000
Amounts due from related parties included in accounts receivable		8,195,000	8,195,000			2,084,000
Amounts payable to related parties included in accounts payable and accrued liabilities		6,788,000	6,788,000			611,000
GCI [Member] | Vessels [Member]
Related Party Transaction [Line Items]
Due from related parties		219,841,000	219,841,000
GCI [Member] | Vessels [Member] | Minimum [Member]
Related Party Transaction [Line Items]
Receivable interest rate			5.00%
Receivable interest rate			Interest at 5% per annum
GCI [Member] | Vessels [Member] | Maximum [Member]
Related Party Transaction [Line Items]
Receivable interest rate			7.00%
Receivable interest rate			Interest at 7% per annum
Technical and other services [Member]
Related Party Transaction [Line Items]
Costs incurred under the management agreements					9,700,000
Dry-dock activities included in technical services [Member]
Related Party Transaction [Line Items]
Costs incurred under the management agreements					421,000
Other services [Member]
Related Party Transaction [Line Items]
Costs incurred under the management agreements					$410,000

Related_party_transactions_Sch

Related party transactions - Schedule of Income or Expenses with Related Parties (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Arrangement fees [Member]
Related Party Transaction [Line Items]
Expenses incurred with related parties	$4,520,000	$6,631,000	$1,790,000
Transaction fees [Member]
Related Party Transaction [Line Items]
Expenses incurred with related parties	7,323,000	3,532,000	123,000
Reimbursed expenses [Member]
Related Party Transaction [Line Items]
Expenses incurred with related parties	237,000	72,000
Interest Income [Member]
Related Party Transaction [Line Items]
Income received from related parties	9,888,000	1,150,000
Management Fees [Member]
Related Party Transaction [Line Items]
Income received from related parties	$913,000	$69,000

Gross_investment_in_lease_Sche

Gross investment in lease - Schedule of Gross Investment in Lease (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Leases [Abstract]
Gross investment in lease	$58,953	$80,123
Current portion	-21,170	-21,170
Gross investment in lease, non-current portion	$37,783	$58,953

Gross_investment_in_lease_Addi

Gross investment in lease - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011
	Vessel
Leases [Abstract]
Term of agreement	5 years
Number of vessels	4
Purchase price of vessels	$5,000,000

Vessels_Schedule_of_Vessels_De

Vessels - Schedule of Vessels (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Property, Plant and Equipment [Line Items]
Cost	$5,990,687	$5,713,085
Accumulated depreciation	894,964	720,814
Net book value	5,095,723	4,992,271
Vessels [Member]
Property, Plant and Equipment [Line Items]
Cost	5,708,685	5,391,713
Accumulated depreciation	894,964	720,814
Net book value	4,813,721	4,670,899
Vessels under construction [Member]
Property, Plant and Equipment [Line Items]
Cost	282,002	321,372
Net book value	$282,002	$321,372

Vessels_Additional_Information

Vessels - Additional Information (Detail) (USD $)	12 Months Ended	0 Months Ended
	Dec. 31, 2012	Jun. 27, 2012	Dec. 31, 2014	Dec. 31, 2013	Jun. 01, 2012
Property, Plant and Equipment [Line Items]
Capitalized interest costs to vessels	$2,983,000		$8,184,000	$2,873,000
Gain (loss) on vessels	9,773,000
Term Loan Credit Facilities [Member]
Property, Plant and Equipment [Line Items]
Term loan					53,000,000
Loan amount outstanding		52,104,000
Gain (loss) on vessels		$9,773,000
Term Loan Credit Facilities [Member] | Vessels [Member]
Property, Plant and Equipment [Line Items]
Leasing period for the vessel		9 years

Deferred_charges_Deferred_Char

Deferred charges - Deferred Charges (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Beginning Balance, Dry-docking	$12,247	$12,694
Cost incurred, Dry-docking	11,318	3,500
Amortization expensed, Dry-docking	-5,059	-3,947
Refinancing expenses and costs, Dry-docking	0	0
Amortization capitalized, Dry-docking	0	0
Ending Balance, Dry-docking	18,506	12,247	12,694
Beginning Balance, Financing fees	41,724	31,122
Cost incurred, Financing fees	19,445	25,131
Amortization expensed, Financing fees	-10,342	-9,477	-8,574
Refinancing expenses and costs, Financing fees	-3,279	-4,038
Amortization capitalized, Financing fees	-1,399	-1,014
Ending Balance, Financing fees	46,149	41,724	31,122
Beginning Balance, Total	53,971	43,816
Cost incurred, Total	30,763	28,631
Amortization expensed, Total	-15,401	-13,424
Refinancing expenses and costs, Total	-3,279	-4,038
Amortization capitalized, Total	-1,399	-1,014
Ending Balance, Total	$64,655	$53,971	$43,816

Deferred_charges_Deferred_Char1

Deferred charges - Deferred Charges (Parenthetical) (Detail) (Leases for five 4500 TEU vessels [Member], USD $)	12 Months Ended
	Dec. 31, 2014
Leases for five 4500 TEU vessels [Member]
Deferred Costs And Other Assets [Line Items]
Deferred financing fees written off	$945,000

Deferred_charges_Additional_In

Deferred charges - Additional Information (Detail) (USD $)	12 Months Ended		0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Apr. 03, 2014	Mar. 27, 2014	Jan. 31, 2014
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Gross proceeds from issuance of senior unsecured notes	$345,000,000
Refinancing expenses and costs	3,279,000	4,038,000
Refinancing expenses and costs	70,000	4,038,000
Term Loan Credit Facilities [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Repayment of credit facility			125,000,000
Revolving Credit Facilities [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Agreement to extend and refinance revolving credit facility		1,000,000,000		0	433,800,000
Senior Unsecured Notes [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Gross proceeds from issuance of senior unsecured notes			345,000,000
Refinancing expenses and costs			$2,334,000

Other_assets_Schedule_of_Other

Other assets - Schedule of Other Assets (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Equity investment in affiliate	$19,555	$4,299
Intangible assets	2,525	2,695
Capital assets	1,579	471
Other	29,794	25,624
Other assets	67,308	106,944
Deposit account over which lessor has first priority interest [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Restricted cash	$13,855	$73,855

Other_assets_Schedule_of_Other1

Other assets - Schedule of Other Assets (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Mar. 14, 2011
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Anticipated investment period (in years)	5 years
Capital contribution	$19,555,000
Percentage of investment in vehicle on equity method	10.80%
Amount of investment comprised of capital contribution	21,408,000	6,408,000
Amount of equity loss on investment	1,853,000	2,109,000
Amount of cash deposit account	0	60,000,000
Maximum [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Minority investment in vehicle during investment period			100,000,000
Maximum [Member] | GCI [Member]
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Line Items]
Equity capital in containership assets			$900,000,000

Deferred_revenue_Deferred_Reve

Deferred revenue - Deferred Revenue (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Deferred Revenue Disclosure [Abstract]
Deferred revenue on time charters	$21,889	$21,099
Deferred interest on lease receivable	4,143	7,903
Other deferred revenue	8,982	2,824
Deferred revenue	35,014	31,826
Current portion	-27,671	-27,683
Deferred revenue	7,343	4,143
Deferred revenue	$35,014	$31,826

Longterm_debt_Schedule_of_Long

Long-term debt - Schedule of Long-Term Debt (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Long-term debt
Long-term debt	$3,382,419,000	$3,241,618,000
Current portion	-298,010,000	-388,159,000
Long-term debt Non Current	3,084,409,000	2,853,459,000
Long Term Debt	3,382,419,000	3,241,618,000
Revolving Credit Facilities [Member]
Long-term debt
Long-term debt	1,301,920,000	2,268,841,000
Long Term Debt	1,301,920,000	2,268,841,000
Term Loan Credit Facilities [Member]
Long-term debt
Long-term debt	1,735,499,000	972,777,000
Long Term Debt	1,735,499,000	972,777,000
Senior Unsecured Notes [Member]
Long-term debt
Long-term debt	345,000,000
Long Term Debt	$345,000,000

Longterm_debt_Schedule_of_Long1

Long-term debt - Schedule of Long-Term Debt (Parenthetical) (Detail) (USD $)	12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2014	Apr. 03, 2014	Dec. 31, 2013	Mar. 27, 2014	Jan. 31, 2014	1-May-14	Jun. 30, 2014	Dec. 24, 2014
Debt Instrument [Line Items]
Gross proceeds from issuance of senior unsecured notes	$345,000,000
Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Credit facilities, maximum aggregate borrowings	2,075,499,000		1,739,497,000
Credit facilities, aggregate borrowings undrawn	340,000,000		766,720,000
Credit facility maturity start date	9-Jul-17
Credit facility maturity end date	23-Apr-25
Weighted average rate of interest, including the margin	2.80%		2.70%
Number of term loan credit facilities	13
Term Loan payments, Description	Term Loan payments are made in quarterly or semi-annual payments commencing three, six or thirty-six months after delivery of the associated newbuilding containership or utilization date.
Term loan, outstanding principal	4,500,000
Repayment of credit facility		125,000,000
Term Loan Credit Facilities [Member] | LIBOR plus margin [Member]
Debt Instrument [Line Items]
Interest rate description	Interest is calculated as one month, three month or six month LIBOR plus a margin per annum
Debt instrument description	At December 31, 2014, the one month, three month and six month LIBOR was 0.2%, 0.2% and 0.3%, respectively (2013-0.2%, 0.2% and 0.4%, respectively) and the margins ranged between 0.4% and 4.8% (2013-0.4% and 4.8%).
Term loan principal outstanding amount	1,614,394,000
Term Loan Credit Facilities [Member] | Three Month LIBOR [Member]
Debt Instrument [Line Items]
LIBOR interest rate	0.20%		0.20%
Term Loan Credit Facilities [Member] | One Month LIBOR [Member]
Debt Instrument [Line Items]
LIBOR interest rate	0.20%		0.20%
Term Loan Credit Facilities [Member] | Six Month LIBOR [Member]
Debt Instrument [Line Items]
LIBOR interest rate	0.30%		0.40%
Senior Unsecured Notes [Member]
Debt Instrument [Line Items]
Interest rate on debt instrument		6.38%
Issuance of senior unsecured notes		13,800,000
Debt instrument price per share		25
Gross proceeds from issuance of senior unsecured notes		345,000,000
Notes, maturity date	30-Apr-19
Export-Import Bank Of Korea [Member] | Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Interest rate margin	0.70%
Term loan principal outstanding amount	116,605,000
Interest 6% [Member] | Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Term loan principal outstanding amount	4,500,000
Interest rate on debt instrument	6.00%
Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
Credit facilities, maximum aggregate borrowings	1,307,046,000		2,388,284,000
Credit facilities, aggregate borrowings undrawn	5,126,000		119,443,000
Number of long-term revolving credit facilities	4
Revolving credit facility amount outstanding			1,000,000,000	0	433,800,000
Revolving credit facility, maturity date			31-May-15
Revolving credit facility, maturity date extended	May 2015 to May 2019
Revolving credit facility, Reduction			340,000,000
Revolving credit facility reduction funded by cash			260,000,000
Cancellation of revolving credit facility				150,000,000
Credit facility maturity start date	30-Apr-15
Credit facility maturity end date	31-Dec-23
Interest rate description	Interest is calculated as one month or three month LIBOR plus a margin per annum
Debt instrument description	At December 31, 2014, the one month and three month LIBOR was 0.2% (2013-0.2%) and the margins ranged between 0.5% and 1.3% (2013-0.5% and 0.9%).
Weighted average rate of interest, including the margin	0.80%		0.80%
Description of the terms of a credit facility arrangement	The Revolver loan payments are made in quarterly or semi-annual payments commencing six or thirty-six months after delivery of the associated newbuilding containership.
Revolving Credit Facilities [Member] | One and Three Month LIBOR [Member]
Debt Instrument [Line Items]
LIBOR interest rate	0.20%		0.20%
Three Hundred And Sixty Four Day Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Credit facilities, maximum aggregate borrowings						100,000,000
Revolving credit facility amount outstanding						100,000,000
European Bank [Member] | Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Credit facilities, LIBOR based term loan							83,000,000
European Bank [Member] | Term Loan Credit Facilities [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Amounts drawn under term loan facilities	0
U.S. Bank and Australian Bank [Member] | Term Loan Credit Facilities [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Credit facilities, LIBOR based term loan								67,040,000
Amounts drawn under term loan facilities	$67,040,000
Minimum [Member] | Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Commitment fee on undrawn amount	0.20%
Minimum [Member] | Term Loan Credit Facilities [Member] | LIBOR plus margin [Member]
Debt Instrument [Line Items]
Interest rate margin	0.40%		0.40%
Minimum [Member] | Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
Interest rate margin	0.50%		0.50%
Commitment fee on undrawn amount	0.20%
Maximum [Member] | Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
Commitment fee on undrawn amount	1.10%
Maximum [Member] | Term Loan Credit Facilities [Member] | LIBOR plus margin [Member]
Debt Instrument [Line Items]
Interest rate margin	4.80%		4.80%
Maximum [Member] | Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
Interest rate margin	1.30%		0.90%
Commitment fee on undrawn amount	0.40%

Longterm_debt_Schedule_of_Mini

Long-term debt - Schedule of Minimum Repayments for Balances Outstanding with Respect to Credit Facility (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long Term Debt	$3,382,419,000	$3,241,618,000
Revolving Credit Facilities [Member]
Debt Instrument [Line Items]
2015	167,593,000
2016	70,417,000
2017	111,201,000
2018	73,355,000
2019	205,188,000
Thereafter	674,166,000
Long Term Debt	1,301,920,000	2,268,841,000
Term Loan Credit Facilities [Member]
Debt Instrument [Line Items]
2015	130,417,000
2016	140,207,000
2017	164,757,000
2018	142,905,000
2019	355,249,000
Thereafter	801,964,000
Long Term Debt	$1,735,499,000

Other_longterm_liabilities_Sch

Other long-term liabilities - Schedule of Other Long-Term Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Other Long Term Liabilities [Abstract]
Long term obligations under capital lease	$214,458	$611,603
Deferred gain on sale-leasebacks	57,627
Other long-term liabilities	272,085	611,603
Current portion	-18,543	-38,930
Total other long-term liabilities	$253,542	$572,673

Other_longterm_liabilities_Sch1

Other long-term liabilities - Schedule of Other Long-Term Liabilities (Parenthetical) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Other Long-Term Liabilities [Line Items]
Amount of cash deposit account	$0	$60,000,000
Carrying value of vessels being funded	315,600,000	766,321,000
Deferred gain on sale leaseback	57,627,000
COSCO Pride - 13100 TEU vessel [Member]
Other Long-Term Liabilities [Line Items]
Terms of leases (in years)	12 years
Financing from lessor	144,185,000
Lease payments include an interest component based on three month LIBOR plus margin percentage	2.60%
COSCO Faith - 13100 TEU vessel [Member]
Other Long-Term Liabilities [Line Items]
Terms of leases (in years)	12 years
Financing from lessor	109,000,000
Lease payments include an interest component based on three month LIBOR plus margin percentage	3.00%
Amount of option to purchase the vessel from the lessor	1
Four 10000 TEU Vessels [Member]
Other Long-Term Liabilities [Line Items]
Proceeds from lease financing arrangements(in Dollars per vessel)	110,000,000
Proceeds from lease financing arrangements in total	440,000,000
Terms of leases	8 years 6 months
Additional terms of leases	2 years
Number of vessels	4
Sale leaseback transaction term description	Under the lease financing arrangements, the Company will sell the vessels to the SPCs and lease the vessels back from the SPCs over a term of approximately 8.5 years, with an option to purchase the vessels at the end of the lease term for a pre-determined fair value purchase price. If the purchase option is not exercised, the lease term will be automatically extended for an additional two years.
Number of vessel lease sold	3
Proceeds from lease financing arrangements in total	330,000,000
Deferred gain on sale leaseback	59,055,000
Total term lease period	10 years 6 months
Leases for five 4500 TEU vessels [Member]
Other Long-Term Liabilities [Line Items]
Terms of leases (in years)	5 years
Amount of cash deposit account	60,000,000
Realized net gain on termination of leases	3,763,000
Deferred financing fees wrote off	945,000
Maximum [Member] | COSCO Pride - 13100 TEU vessel [Member]
Other Long-Term Liabilities [Line Items]
Outstanding balance at end of lease term	$48,000,000

Other_longterm_liabilities_Bas

Other long-term liabilities - Based on Maximum Amounts Funded Payments Under Leases Due to Lessors (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Other Long Term Liabilities [Abstract]
2015	$20,226
2016	23,044
2017	23,387
2018	23,731
2019	24,101
Thereafter	146,794
Capital Leases, Future Minimum payments Due, Total	261,283
Less amounts representing interest	-46,825
Capital Lease Obligation	$214,458

Share_Capital_Additional_Infor

Share Capital - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended			1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	22-May-14	Nov. 25, 2013	Jan. 19, 2012	Sep. 30, 2013	Nov. 08, 2013	Dec. 13, 2012	Feb. 13, 2014	Jan. 28, 2014	Jan. 30, 2014	Feb. 26, 2012	Sep. 11, 2013
Class of Stock [Line Items]
Dividend reinvestment program discount rate percentage	3.00%
Value of stock repurchased		$8,950,000	$172,812,000
Preferred stock, authorized	150,000,000	65,000,000
Preferred stock outstanding	24,170,531	18,970,531
Preferred shares issued	24,170,531	18,970,531
Gross proceeds of issuance of preferred shares	130,415,000	47,862,000	74,700,000
Minimum [Member]
Class of Stock [Line Items]
Preferred stock, authorized											65,000,000
Capital stock, authorized											290,000,100
Maximum [Member]
Class of Stock [Line Items]
Preferred stock, authorized											150,000,000
Capital stock, authorized											375,000,100
Class A Common Shares [Member]
Class of Stock [Line Items]
Common stock shares, Authorized	200,000,000	200,000,000
Common stock shares, Issued	96,662,928	69,208,888			3,500,000
Common stock shares, Outstanding	96,662,928	69,208,888
Maximum sales proceeds from at the market offering				75,000,000
Number of shares issued	206,600
Gross proceeds from issue of shares					77,000,000
Class A common shares price per share					$22
Value of shares authorized for repurchase													50,000,000
Number of shares repurchased			148,101			11,300,000
Value of stock repurchased			2,203,000			170,609,000
Repurchase price per share						$15
Stock re-purchase fee and expenses						1,110,000
Number of Class A common shares issued upon conversion of Series A preferred shares												23,177,175
Class A Common Shares [Member] | At-the-Market [Member]
Class of Stock [Line Items]
Gross proceeds from issue of shares	4,733,000
Convertible Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock outstanding												200,000
Series C Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, authorized	40,000,000
Preferred stock outstanding	13,665,531
Dividend rate percentage	9.50%						9.50%
Redemption price per share	$25
Increase in dividend rate payable quarterly	1.25
Expiration of share repurchase authorization	2014-07
Preferred shares issued	13,665,531
Series C Preferred Shares [Member] | Prior to January 30, 2016 [Member]
Class of Stock [Line Items]
Aggregate maximum dividend rate payable per annum	25.00%
Series C Preferred Shares [Member] | After January 30, 2016 [Member]
Class of Stock [Line Items]
Aggregate maximum dividend rate payable per annum	30.00%
Series C Preferred Shares [Member] | Open Market Repurchase Plan [Member]
Class of Stock [Line Items]
Value of shares authorized for repurchase														25,000,000
Number of shares repurchased		14,469					320,000
Value of stock repurchased		390,000,000					8,560,000,000
Repurchase price per share							26.5
Series D Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, authorized	20,000,000
Preferred stock outstanding	5,105,000
Dividend rate percentage									7.95%
Redemption price per share	$25
Preferred shares issued	5,105,000							2,000,000	3,105,000
Gross proceeds of issuance of preferred shares								50,000,000	77,625,000
Series E Preferred Shares [Member]
Class of Stock [Line Items]
Preferred stock, authorized	15,000,000
Preferred stock outstanding	5,400,000
Dividend rate percentage										8.25%
Redemption price per share										$25
Preferred shares issued	5,400,000									5,400,000
Gross proceeds of issuance of preferred shares										$135,000,000
Common Class B [Member]
Class of Stock [Line Items]
Common stock shares, Authorized	25,000,000	25,000,000
Common stock shares, Issued
Common stock shares, Outstanding
Class C common Shares [Member]
Class of Stock [Line Items]
Common stock shares, Authorized	100	100
Common stock shares, Issued
Common stock shares, Outstanding

Share_Capital_Schedule_of_Pref

Share Capital - Schedule of Preferred Shares Outstanding (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Nov. 08, 2013	Dec. 13, 2012	Feb. 13, 2014
In Thousands, except Share data, unless otherwise specified
Class of Stock [Line Items]
Shares Authorized	150,000,000	65,000,000
Shares Issued	24,170,531	18,970,531
Series A Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	315,000
Liquidation preference		344,262
Series B Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	260,000
Series C Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	40,000,000
Shares Issued	13,665,531
Liquidation preference	341,638	341,638
Series D Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	20,000,000
Shares Issued	5,105,000		2,000,000	3,105,000
Liquidation preference	127,625	127,625
Series E Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	15,000,000
Shares Issued	5,400,000				5,400,000
Liquidation preference	135,000
Series R Preferred Shares [Member]
Class of Stock [Line Items]
Shares Authorized	1,000,000

Earnings_per_share_Schedule_of

Earnings per share - Schedule of Reconciliation of Numerator and Denominator Used in Basic and Diluted EPS Computations (Detail) (USD $)	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Net earnings	$131,247	$299,028	$121,305
Earnings attributable to common shareholders	74,417	219,199	52,689
Convertible Series A preferred shares		38,390
Earnings attributable to common shareholders plus assumed conversion	74,417	257,589	52,689
Earnings attributable to common shareholders, shares	93,402,000	65,273,000	62,923,240
Share-based compensation, shares	131,000	306,000	238,000
Contingent consideration, shares	117,000	567,000	1,236,000
Shares held in escrow		47,000	545,000
Convertible Series A preferred shares, shares		21,641,000
Earnings attributable to common shareholders plus assumed conversion, shares	93,650,000	87,834,000	64,942,240
Earnings attributable to common shareholders, per share amount	$0.80	$3.36	$0.84
Earnings attributable to common shareholders plus assumed conversion, per share amount	$0.79	$2.93	$0.81
Series A Preferred Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred share dividends	-3,395	-38,390	-34,195
Series C Preferred Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Series C preferred share repurchases		-660
Preferred share dividends	-33,623	-34,035	-34,112
Series D Preferred Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred share dividends	-10,036	-6,744	-309
Series E Preferred Shares [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Preferred share dividends	($9,776)

Sharebased_compensation_Additi

Share-based compensation - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 07, 2012	Jun. 12, 2014
				Tranches
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shares of common stock reserved for issuance under the plan	2,000,000
Expiration period of plan, years	10 years
Remaining shares left for issuance under this plan	578,598	764,848
Share-based compensation expenses	$7,701,000	$14,004,000	$3,278,000
Total unrecognized compensation costs relating to unvested share-based compensation awards	3,041,000	6,472,000
Expected to be recognized over a weighted average period	18 months
Granted, shares		1,664,457	5,674,148
Share-based transaction fees capitalized to vessels	3,662,000	1,766,000	62,000
Deferred financing fees	64,655,000	53,971,000	43,816,000
Transaction fees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses incurred	7,323,000	3,532,000	123,000
Arrangement fees [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expenses incurred	4,520,000	6,631,000	1,790,000
Deferred financing fees	2,260,000	2,666,000	895,000
Restricted shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	1 year
Total fair value of shares vested	831,000	935,000	563,000
Total fair value of shares cancelled		71,000
Granted, shares	43,936	54,990	63,653
Phantom share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Outstanding phantom share units vested and available for exchange	560,000	460,000
Granted, shares	70,000	95,000	40,000
Stock appreciation rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conditions for exercise of tranches				If the fair market value of the common shares equals or exceeds the applicable base price for each tranche for any 20 consecutive trading days on or before the expiration date of each tranche.
Granted, shares		1,664,457	5,674,148	5,674,148
Number of tranches	3			3
Stock appreciation rights (SARs) [Member] | March 27, 2013 Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Conditions for exercise of tranches	If the fair market value of the common shares equals or exceeds the applicable base price for each tranche for any 20 consecutive trading days on or before the expiration date of each tranche.
Retention requirement description	The common shares received on the exercise of SARs are subject to a retention requirement where the Participant is required to retain ownership of 50% of the net after tax number of shares until the later of March 22, 2018 or 120 days after the exercise date.
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period					3 years
Granted, shares	72,314				72,314
Retention requirement description	The restricted stock units generally vest over three years, in equal one-third amounts on each anniversary date of the date of the grant.
2012 Restricted Stock Unit Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares					39,399
2013 Restricted Stock Unit Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted, shares					32,915
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expenses	$600,000	$600,000	$750,000

Sharebased_compensation_Summar

Share-based compensation - Summary of Outstanding Restricted Shares, Phantom Share Units, SARs and Restricted Stock Units (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014	Dec. 07, 2012	Jun. 12, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted	1,664,457	5,674,148
Restricted shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of shares	63,653	43,200	48,880
Granted	54,990	63,653	43,936
Vested	-65,578	-43,200	-48,880
Cancelled	-4,185
Ending balance, Number of shares	48,880	63,653	43,936
Beginning balance, W.A. grant date FV	14.17	13.04	$17.01
Granted	17.01	14.17	$22.57
Vested	14.25	13.04	$17.01
Cancelled	17.01
Ending balance, W.A. grant date FV	17.01	14.17	$22.57
Phantom share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of shares	562,000	522,000	657,000
Granted	95,000	40,000	70,000
Exchanged			-20,000
Ending balance, Number of shares	657,000	562,000	707,000
Beginning balance, W.A. grant date FV	13.13	12.78	$14.02
Granted	19.3	17.68	$23.04
Exchanged			$19
Ending balance, W.A. grant date FV	14.02	13.13	$14.77
Stock appreciation rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning balance, Number of shares	5,674,148		7,072,945
Granted	1,664,457	5,674,148		5,674,148
Exercised	-241,906		-1,193,529
Cancelled	-23,754
Ending balance, Number of shares	7,072,945	5,674,148	5,879,416
Beginning balance, W.A. grant date FV	2.03		$2.32
Granted	3.51	2.03
Exercised	3.65		$2.42
Cancelled	3.51
Ending balance, W.A. grant date FV	2.32	2.03	$2.30
Restricted stock units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			72,314		72,314
Vested			-37,238
Ending balance, Number of shares			35,076
Granted			$23.03
Vested			$23.03
Ending balance, W.A. grant date FV			$23.03

Sharebased_compensation_Schedu

Share-based compensation - Schedule of Assumptions to Calculate Fair Value of Stock Appreciation Rights (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Average expected term	3 years 9 months 18 days	1 year 6 months
Expected volatility	39.73%	40.12%
Dividend yield	4.97%	5.74%
Average risk free rate	0.50%	0.47%

Sharebased_compensation_Schedu1

Share-based compensation - Schedule of Information about Three Tranches of SARs Granted (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of SARs		1,664,457	5,674,148
Tranche 1 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Base price	$21.50
Expiration date	7-Dec-15
Number of SARs		531,885	1,846,154
Tranche 2 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Base price	$24
Expiration date	7-Dec-16
Number of SARs		556,946	1,898,734
Tranche 3 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Base price	$26.50
Expiration date	7-Dec-17
Number of SARs		575,626	1,929,260

Other_information_Schedule_of_

Other information - Schedule of Accounts Payable and Accrued Liabilities (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Due to related parties (note 4)	$6,788	$611
Accrued interest	20,723	22,273
Accounts payable and other accrued liabilities	37,697	42,750
Accounts payable and accrued liabilities, Total	$65,208	$65,634

Other_information_Schedule_of_1

Other information - Schedule of Supplemental Cash Flow Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplemental Cash Flow Information [Line Items]
Interest paid on debt	$91,450,000	$59,999,000	$64,123,000
Interest received	1,211,000	1,265,000	634,000
Undrawn credit facility fee paid	3,512,000	1,656,000	900,000
Non-cash transactions:
Long-term debt for vessels under construction	161,420,000	54,080,000	71,400,000
Dividend reinvestment	64,697,000	31,961,000	7,168,000
Loan repayment for vessels under construction	29,680,000	6,560,000
Vessel reallocation (note 4)	11,533,000
Fair value of financial instruments	50,278,000
Capital contribution through loans to affiliate	15,000,000
Other long-term liabilities for vessels under construction			84,787,000
Acquisition of the Manager for shares, excluding cash received			82,607,000
Proceeds on sale of vessel			52,104,000
Arrangement and Transaction Fees [Member]
Non-cash transactions:
Arrangement and transaction fees (note 14)	6,753,000	3,342,000	1,141,000
Series A Preferred Shares [Member]
Non-cash transactions:
Dividends on Series A preferred shares	$3,395,000	$38,390,000	$34,195,000

Commitments_and_contingent_obl2

Commitments and contingent obligations - Schedule of Future Minimum Revenues to be Received on Committed Agreements (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Leases [Abstract]
2015	$799,800
2016	836,448
2017	786,780
2018	771,564
2019	743,100
Thereafter	2,482,431
Future minimum revenues receivable	$6,420,123

Commitments_and_contingent_obl3

Commitments and contingent obligations - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014
Leases [Line Items]
Percentage of future minimum revenues utilization	100.00%
Operating leases, future minimum payments due	$328,331,000
Vessels [Member]
Leases [Line Items]
Operating leases, future minimum payments due	320,020,000
Operating leases, start year	2015
Operating leases, expiration year	2025
Office Space [Member]
Leases [Line Items]
Operating leases, future minimum payments due	$8,311,000
Operating leases, start year	2015
Operating leases, expiration year	2019

Commitments_and_contingent_obl4

Commitments and contingent obligations - Schedule of Outstanding Commitments for Installment Payments for Vessels (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Commitments and Contingencies Disclosure [Abstract]
2015	$651,469
2016	402,622
Purchase obligations for additional vessels	$1,054,091

Commitments_and_contingent_obl5

Commitments and contingent obligations - Schedule of Commitment Under Operating Leases (Detail) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Leases [Abstract]
2015	$32,794
2016	33,079
2017	33,504
2018	33,172
2019	32,738
Thereafter	163,044
Operating leases, future minimum payments due	$328,331

Concentrations_Schedule_of_Rev

Concentrations - Schedule of Revenue Derived from Customers (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenue, Major Customer [Line Items]
Revenue	$717,170	$677,090	$660,794
COSCON [Member]
Revenue, Major Customer [Line Items]
Revenue	303,357	301,842	281,469
CSCL Asia [Member]
Revenue, Major Customer [Line Items]
Revenue	126,399	134,434	151,658
Hapag Lloyd [Member]
Revenue, Major Customer [Line Items]
Revenue	77,675	65,463	58,980
K-Line [Member]
Revenue, Major Customer [Line Items]
Revenue	76,130	76,148	76,359
Other [Member]
Revenue, Major Customer [Line Items]
Revenue	$133,609	$99,203	$92,328

Financial_instruments_Addition

Financial instruments - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Carrying value, long-term debt	$3,382,419,000	$3,241,618,000
Fair value of other long-term liabilities, excluding deferred gains	217,134,000	587,733,000
Carrying value of other long-term liabilities, excluding deferred gains	214,458,000	611,603,000
Estimated accumulated other comprehensive loss expected to be reclassified to net earnings	4,402,000
Fair value of financial instruments liability	26,625,000	49,534,000
Restricted cash	1,100,000
Swaption Counterparty B [Member]
Derivative [Line Items]
Derivative, fixed interest rate	1.18%
Fixed per annum rate swapped for LIBOR	0.50%
Derivative, notional amount	200,000,000
Effective date	2-Mar-17
Ending date	2-Mar-27
Foreign Exchange Contract [Member]
Derivative [Line Items]
Notional amount on foreign exchange forward contract	14,200,000	12,200,000
Fair value of financial instruments liability	638,000	286,000
Revolving and Term Loan Credit Facilities [Member]
Derivative [Line Items]
Fair value, long-term debt	2,911,330,000	2,897,650,000
Carrying value, long-term debt	3,037,419,000	3,241,618,000
Senior Unsecured Notes [Member]
Derivative [Line Items]
Fair value, long-term debt	342,240,000	0
Carrying value, long-term debt	$345,000,000	$0

Financial_instruments_Schedule

Financial instruments - Schedule of Outstanding Interest Rate Derivatives (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Jan. 30, 2014
5.6400% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.64%
Derivative, notional amount	$714,500,000
Effective date	31-Aug-07
Ending date	31-Aug-17
5.4200% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.42%
Derivative, notional amount	438,462,000
Effective date	6-Sep-07
Ending date	31-May-24
5.9450% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.95%	5.95%
Derivative, notional amount	266,944,000
Effective date	30-Jan-14
Ending date	31-May-19
5.6000% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.60%
Derivative, notional amount	175,200,000
Effective date	23-Jun-10
Ending date	23-Dec-21
5.0275% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.03%
Derivative, notional amount	111,000,000
Effective date	31-May-07
Ending date	30-Sep-15
5.5950% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.60%
Derivative, notional amount	103,500,000
Effective date	28-Aug-09
Ending date	28-Aug-20
5.2600% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.26%
Derivative, notional amount	103,500,000
Effective date	3-Jul-06
Ending date	26-Feb-21
5.2000% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.20%
Derivative, notional amount	80,640,000
Effective date	18-Dec-06
Ending date	2-Oct-15
5.4975% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.50%
Derivative, notional amount	52,400,000
Effective date	31-Jul-12
Ending date	31-Jul-19
5.1700% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.17%
Derivative, notional amount	24,000,000
Effective date	30-Apr-07
Ending date	29-May-20
5.8700% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.87%
Effective date	31-Aug-17
Ending date	28-Nov-25
Maximum [Member] | 5.6400% [Member]
Derivative [Line Items]
Derivative, notional amount	714,500,000
Maximum [Member] | 5.4200% [Member]
Derivative [Line Items]
Derivative, notional amount	438,462,000
Maximum [Member] | 5.9450% [Member]
Derivative [Line Items]
Derivative, notional amount	266,944,000
Maximum [Member] | 5.6000% [Member]
Derivative [Line Items]
Derivative, notional amount	175,200,000
Maximum [Member] | 5.0275% [Member]
Derivative [Line Items]
Derivative, notional amount	111,000,000
Maximum [Member] | 5.5950% [Member]
Derivative [Line Items]
Derivative, notional amount	103,500,000
Maximum [Member] | 5.2600% [Member]
Derivative [Line Items]
Derivative, notional amount	103,500,000
Maximum [Member] | 5.2000% [Member]
Derivative [Line Items]
Derivative, notional amount	80,640,000
Maximum [Member] | 5.4975% [Member]
Derivative [Line Items]
Derivative, notional amount	52,400,000
Maximum [Member] | 5.1700% [Member]
Derivative [Line Items]
Derivative, notional amount	24,000,000
Maximum [Member] | 5.8700% [Member]
Derivative [Line Items]
Derivative, notional amount	$620,390,000

Financial_instruments_Schedule1

Financial instruments - Schedule of Outstanding Interest Rate Derivatives (Parenthetical) (Detail) (USD $)	0 Months Ended	12 Months Ended
	Jan. 30, 2014	Dec. 31, 2014	Jan. 30, 2014
Swaption Counterparty A [Member]
Derivative [Line Items]
Derivative, notional amount		106,800,000
Fixed per annum rate swapped for LIBOR		5.26%
Effective date		28-Feb-14
Ending date		26-Feb-21
5.9450% [Member]
Derivative [Line Items]
Derivative, notional amount		266,944,000
Fixed per annum rate swapped for LIBOR	5.95%	5.95%	5.95%
Effective date		30-Jan-14
Ending date		31-May-19
5.1750% [Member]
Derivative [Line Items]
Fixed per annum rate swapped for LIBOR	5.18%		5.18%
Effective date		16-Jul-12
Early termination loss	$4,492,000
Derivative termination date		30-Jan-14

Financial_instruments_Schedule2

Financial instruments - Schedule of Losses Reclassified from Accumulated Other Comprehensive Loss into Earnings (Detail) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Gain/(Loss) on derivatives recognized in net earnings:
Change in fair value of financial instruments	($105,694)	$60,504	($135,998)
Interest Expense [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Loss reclassified from AOCL to net earnings
Depreciation and amortization/Interest expense	-4,259	-5,330	-8,310
Depreciation and Amortization [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member]
Loss reclassified from AOCL to net earnings
Depreciation and amortization/Interest expense	($1,052)	($882)	($836)

Financial_instruments_Schedule3

Financial instruments - Schedule of Derivatives (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair value of asset and liability derivatives:
Fair value of financial instruments asset	$37,677	$60,188
Fair value of financial instruments liability	$395,443	$425,375

Financial_instruments_Schedule4

Financial instruments - Schedule of Financial Instruments, Effect of the Master Netting Agreement (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Derivative Instrument Detail [Abstract]
Derivative assets, Gross amounts of recognized assets and liabilities	$37,677	$60,188
Derivative liabilities, Gross amounts of recognized assets and liabilities	395,443	425,375
Net asset (liability)	-357,766	-365,187
Derivative assets, Amounts subject to master netting agreement	26,625	49,534
Derivative liabilities, Amounts subject to master netting agreement	26,625	49,534
Derivative assets, Net amount	11,052	10,654
Derivative liabilities, Net amount	368,818	375,841
Net asset (liability)	($357,766)	($365,187)

Subsequent_events_Additional_I

Subsequent events - Additional Information (Detail) (USD $)	12 Months Ended			0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jan. 13, 2015
Subsequent Event [Line Items]
Dividends distribution was paid in cash	$62,310,000	$44,379,000	$51,772,000
Dividend reinvestment	64,697,000	31,961,000	7,168,000
Common Shares [Member]
Subsequent Event [Line Items]
Dividends declared date	13-Jan-15
Dividend reinvestment	31,000	16,000	5,000
Series C Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends on preferred shares			33,250,000
Dividends declared date	13-Jan-15
Series D Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends declared date	13-Jan-15
Series E Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends declared date	13-Jan-15
Series C, Series D, and Series E Preferred Share [Member]
Subsequent Event [Line Items]
Dividends on preferred shares	50,443,000
Subsequent Events [Member]
Subsequent Event [Line Items]
Dividends on common share, per share				$0.35
Dividends, common stock				33,377,000
Dividends distribution was paid in cash				16,310,000
Subsequent Events [Member] | Common Shares [Member]
Subsequent Event [Line Items]
Dividends date paid				30-Jan-15
Dividends date of record				22-Jan-15
Dividend reinvestment				17,067,000
Subsequent Events [Member] | Series C Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends on preferred shares, per share				$0.59
Dividends date paid				30-Jan-15
Dividends date of record				29-Jan-15
Subsequent Events [Member] | Series D Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends on preferred shares, per share				$0.50
Dividends date paid				30-Jan-15
Dividends date of record				29-Jan-15
Subsequent Events [Member] | Series E Preferred Shares [Member]
Subsequent Event [Line Items]
Dividends on preferred shares, per share				$0.52
Dividends date paid				30-Jan-15
Dividends date of record				29-Jan-15
Subsequent Events [Member] | Series C, Series D, and Series E Preferred Share [Member]
Subsequent Event [Line Items]
Dividends on preferred shares				$13,435,000