Long-Term Incentive Plan (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jan. 31, 2015	Apr. 30, 2008
Long-Term Incentive Plan
Amortization related to shares issued to design and construction employees	$ 165	$ 114
Vesting of restricted stock presented on statement of equity	(1,169)
Amortization of deferred stock compensation	2,895	1,372
Restricted Shares and Performance awards
Long-Term Incentive Plan
Compensation Expense, including forfeitures	4,432	2,036
Net-settle adjustment	(5,766)
Amortization related to shares issued to design and construction employees	165
Vesting of restricted stock presented on statement of equity	(1,169)
Restricted Shares and Performance awards | Minimum
Long-Term Incentive Plan
Vesting period	3 years
Restricted Shares and Performance awards | Maximum
Long-Term Incentive Plan
Vesting period	5 years
Restricted Shares and Performance awards | Kenneth E. Cruse
Long-Term Incentive Plan
Compensation Expense, including forfeitures			2,500
Amortization of deferred stock compensation			$ 1,600
Stock Options | Robert A. Alter
Stock options
Number of nonqualified stock options approved by the compensation committee of the Company's board of directors (in shares)				200,000
Exercise price of options vested (in dollars per share)	$ 17.71			$ 17.71