Summary of Significant Accounting Policies (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income (loss) - numerator
Net income (loss)	$ 110,771us-gaap_NetIncomeLoss	$ 45,094us-gaap_NetIncomeLoss	$ (33,261)us-gaap_NetIncomeLoss
Less dividends to Class B shareholders - distributed earnings	0us-gaap_DistributedEarnings	0us-gaap_DistributedEarnings	(28)us-gaap_DistributedEarnings
Undistributed earnings (loss)	$ 110,771us-gaap_UndistributedEarnings	$ 45,094us-gaap_UndistributedEarnings	$ (33,289)us-gaap_UndistributedEarnings
Weighted average common shares outstanding - denominator
Weighted average common shares outstanding for basic earnings (loss) per share	70,229,000	58,777,000	53,957,000
Diluted	70,906,000	58,929,000	53,957,000
Class A [Member]
Weighted average common shares outstanding - denominator
Weighted average common shares outstanding for basic earnings (loss) per share	70,229,000	58,777,000	53,852,000
Dilutive effect of options and restricted stock units	677,000	152,000	0
Diluted	70,906,000	58,929,000	53,852,000
Basic
Distributed earnings (usd per share)	$ 0.00	$ 0.00	$ 0.00
Undistributed (loss) earnings (usd per share)	$ 1.58	$ 0.77	$ (0.62)
Total (usd per share)	$ 1.58	$ 0.77	$ (0.62)
Diluted
Distributed earnings (usd per share)	$ 0.00	$ 0.00	$ 0.00
Undistributed (loss) earnings (usd per share)	$ 1.56	$ 0.77	$ (0.62)
Total (usd per share)	$ 1.56	$ 0.77	$ (0.62)
Class B [Member]
Weighted average common shares outstanding - denominator
Weighted average common shares outstanding for basic earnings (loss) per share	0	0	105,000
Dilutive effect of options and restricted stock units	0	0	105,000
Basic
Distributed earnings (usd per share)	$ 0.00	$ 0.00	$ 0.27
Undistributed (loss) earnings (usd per share)	$ 0.00	$ 0.00	$ (0.62)
Total (usd per share)	$ 0.00	$ 0.00	$ (0.35)
Diluted
Distributed earnings (usd per share)	$ 0.00	$ 0.00	$ 0.27
Undistributed (loss) earnings (usd per share)	$ 0.00	$ 0.00	$ (0.62)
Total (usd per share)	$ 0.00	$ 0.00	$ (0.35)
Stock options [Member]
Diluted
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			1,067,069
Restricted Stock Units (RSUs) [Member]
Diluted
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			162,368
Restricted stock [Member]
Diluted
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount			305,807

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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