Employee Benefits - Multiemployer Plans (Details) (Multiemployer Plans, Pension, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
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	$ 534		$ 486		$ 336
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	438		400		331
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	856		142		0
Expiration of Collective Bargaining Agreement	Dec. 31, 2014
Alaska Laborers Trust Fund [Member]
Multiemployer Plans [Line Items]
Certified Zone Status	Orange	[1]	NA	[1]
Contributions	$ 0		$ 0		$ 0
Expiration of Collective Bargaining Agreement	Dec. 31, 2015

[1] The most recent PPA zone status available in 2013 and 2012 is for the plan's year end during 2012 and 2011, 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.