Noncontrolling Interests Redeemable Noncontrolling Interests Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	[1]	Jun. 30, 2017	[1]	Mar. 31, 2017		Dec. 31, 2016		Sep. 30, 2016	[1]	Jun. 30, 2016	[1]	Mar. 31, 2016		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Redeemable Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interests, Equity, Carrying Amount, Beginning of Period							$ 16,972										$ 16,972
Nonredeemable Noncontrolling Interest, Beginning of Period							4,161										4,161
Net Income (Loss) Attributable to Noncontrolling Interest	$ 1,278	[1]	$ 1,074		$ 1,150		966	[1]	$ 1,147	[1]	$ 1,110		$ 989		$ 911	[1]	4,468	$ 4,157	$ 4,407
Redeemable Noncontrolling Interests, Equity, Carrying Amount, End of Period	17,461								16,972								17,461	16,972
Nonredeemable Noncontrolling Interest, End of Period	5,186								4,161								5,186	4,161
Anchor [Member]
Redeemable Noncontrolling Interest [Line Items]
Nonredeemable Noncontrolling Interest, Beginning of Period							2,000										2,000
Nonredeemable Noncontrolling Interest, End of Period	2,900								2,000								2,900	2,000
Redeemable Noncontrolling Interest [Member]
Redeemable Noncontrolling Interest [Line Items]
Redeemable Noncontrolling Interests, Equity, Carrying Amount, Beginning of Period							16,972								18,088		16,972	18,088	20,905
Net Income (Loss) Attributable to Noncontrolling Interest																	3,354	3,204	3,575
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders																	(3,277)	(3,112)	(4,189)
Redeemable Noncontrolling Interest Increase, Purchase or Sale of Additional Ownership Interest																			(1,666)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests																	235	(765)
Noncontrolling Interest, Increase from Subsidiary Equity Issuance																	0	0	(1,652)
Amortization of Noncontrolling Interest Equity Compensation																	413	449	0
Noncontrolling Interest, Period Increase (Decrease)																	(236)	(892)	1,115
Redeemable Noncontrolling Interests, Equity, Carrying Amount, End of Period	17,461								16,972								17,461	16,972	18,088
Noncontrolling Interest [Member]
Redeemable Noncontrolling Interest [Line Items]
Nonredeemable Noncontrolling Interest, Beginning of Period							$ 4,161								$ 3,393		4,161	3,393	386
Net Income (Loss) Attributable to Noncontrolling Interest																	1,114	953	832
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders																	(1,083)	(942)	(422)
Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests																	85	(134)	419
Noncontrolling Interest, Increase from Subsidiary Equity Issuance																	0	0	1,652
Amortization of Noncontrolling Interest Equity Compensation																	935	747	472
Noncontrolling Interest, Period Increase (Decrease)																	(26)	144	54
Nonredeemable Noncontrolling Interest, End of Period	$ 5,186								$ 4,161								$ 5,186	$ 4,161	$ 3,393

[1] Due to rounding, the sum of the four quarters may not add to the year to date total.