The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

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The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

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Number of shares issued for each share of convertible preferred stock that is converted.

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The per share liquidation preference (or restrictions) of nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) that has a preference in involuntary liquidation considerably in excess of the par or stated value of the shares. The liquidation preference is the difference between the preference in liquidation and the par or stated values of the share.

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Face amount or stated value per share of preferred stock nonredeemable or redeemable solely at the option of the issuer.

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The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Number of share instruments newly issued under a share-based compensation plan.

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Number of shares issued which are neither cancelled nor held in the treasury.

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Amount of stock repurchase plan authorized.

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Amount remaining of a stock repurchase plan authorized.

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Number of shares that have been repurchased during the period and are being held in treasury.

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Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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-Name Regulation S-X (SX)

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Shareholders' equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended	41 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Aug. 01, 2011	Jul. 31, 2008
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Repurchase of common stock (in shares)		4,786,521us-gaap_TreasuryStockSharesAcquired
Common stock, shares authorized (in shares)		195,000,000us-gaap_CommonStockSharesAuthorized	195,000,000us-gaap_CommonStockSharesAuthorized	195,000,000us-gaap_CommonStockSharesAuthorized
Stock repurchase program, authorized amount					$ 60,000
Treasury stock acquired, Aggregate purchase price	4,033	49,924
Stock repurchase program, Remaining authorized repurchase amount		$ 10,076	10,076
Series A Preferred stock, shares authorized (in shares)		5,000,000us-gaap_PreferredStockSharesAuthorized	5,000,000us-gaap_PreferredStockSharesAuthorized	5,000,000us-gaap_PreferredStockSharesAuthorized
Series A Preferred stock, shares issued (in shares)		160,000us-gaap_PreferredStockSharesIssued	160,000us-gaap_PreferredStockSharesIssued	160,000us-gaap_PreferredStockSharesIssued		160,000us-gaap_PreferredStockSharesIssued
Preferred Stock, Par or Stated Value Per Share		$ 0.01	0.01	0.01
Preferred Stock, Liquidation Preference Per Share		$ 0.01	0.01
Conversion of convertible preferred stock (in shares)		100	100
Series A Convertible Preferred Stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance	80,718		79,620	80,283
Repurchase of common stock (in shares)	0
Conversion of convertible preferred stock (in shares)	(435)		(1,479)	(663)
Issuance for share-based compensation plans (in shares)	0		0	0
Shares, Ending balance	80,283	78,141	78,141	79,620
Treasury stock, at cost [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance	4,386,521		4,786,521	4,786,521
Repurchase of common stock (in shares)	400,000
Conversion of convertible preferred stock (in shares)	0		0	0
Issuance for share-based compensation plans (in shares)	0		0	0
Shares, Ending balance	4,786,521	4,786,521	4,786,521	4,786,521
Common stock [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares, Beginning balance	88,844,327		88,710,277	88,548,637
Repurchase of common stock (in shares)	(400,000)
Conversion of convertible preferred stock (in shares)	43,556		147,952	66,244
Issuance for share-based compensation plans (in shares)	60,754		206,353	95,396
Shares, Ending balance	88,548,637	89,064,582	89,064,582	88,710,277