Employee Benefits - Multiemployer Plans (Details) (Multiemployer Plans, Pension, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
International Union of Operating Engineers-Employers Construction Industry Retirement Plan
Multiemployer Plans [Line Items]
Employer Identification Number	916028571
Certified Zone Status	Green	[1]	Green	[1]
Contributions	$ 486		$ 336		$ 124
Expiration of Collective Bargaining Agreement	Dec. 31, 2015
Associated General Contractors of Washington Carpenter, Piledrivers, and Millwrights
Multiemployer Plans [Line Items]
Employer Identification Number	916029051
Certified Zone Status	Green	[1]	Green	[1]
Contributions	400		331		84
Expiration of Collective Bargaining Agreement	Dec. 31, 2015
Alaska Carpenters Trust Fund
Multiemployer Plans [Line Items]
Employer Identification Number	920120866
Certified Zone Status	Green	[1]	Green	[1]
Contributions	$ 142		$ 0		$ 0
Expiration of Collective Bargaining Agreement	Dec. 31, 2014

[1] The most recent PPA zone status available in 2012 and 2011 is for the plan's year end during 2011 and 2010, respectively. Zone status is based on information received from the plan and is indicative of the plans funding status. Among other factors, plans in the red zone are generally less than 65 percent funded, plans in the orange zone are less than 80 percent funded and have an Accumulated Funding Deficiency in the current year or projected into the next six years, plans in the yellow zone are less than 80 percent funded, and plans in the green zone are at least 80 percent funded.