Dividends Declared and Paid (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended	12 Months Ended	0 Months Ended
Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 20, 2015
Cash dividends declared per common share	$ 0.25	$ 0.25	$ 0	$ 0	$ 0.50	$ 0.00	$ 0.00
Payments of cash dividends to stockholders					$ 56,988us-gaap_PaymentsOfDividendsCommonStock	$ 0us-gaap_PaymentsOfDividendsCommonStock	$ 0us-gaap_PaymentsOfDividendsCommonStock
Subsequent events
Cash dividends declared per common share								$ 0.25

Amount of cash outflow in the form of ordinary dividends to common shareholders of the parent entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration