Share-based Compensation and Non-Qualified Deferred Compensation Plan (NQDC diversified share awards rollforward) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Share-based Compensation [Abstract]
Balance at December 31, 2015	$ 79,364
Change in classification	6,688	$ 4,678
Change in redemption value	11,445	(1)
Diversification of share awards (292 shares)	(25,017)	$ (3,020)	$ (3,600)
Balance at June 30, 2016	$ 72,480		$ 79,364

Change in the value of each type or class of stock classified as temporary equity during the period. The redemption requirement does not constitute an unconditional obligation that will be settled in a variable number of shares constituting a monetary value predominantly indexed to (a) a fixed monetary amount known at inception, (b) an amount inversely correlated with the residual value of the entity, or (c) an amount determined by reference to something other than the fair value of issuer's stock. Does not include mandatorily redeemable stock. The exception is if redemption is required upon liquidation or termination of the reporting entity.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (27)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 480
-SubTopic 10
-Section S99
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=65877616&loc=d3e177068-122764

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